bluuebunny/crossref_metadata_2025 huggingface dataset:
Egg‐float ridge number in Anopheles stephensi: ecological variation and genetic analysis
Authors: SUBBARAO SARALA K. , VASANTHA K. , ADAK T. , SHARMA V. P. , CURTIS C. F.
Published: March 2008

Abstract. Eight Indian laboratory stocks of Anopheles stephensi Liston could be grouped into three categories with, respectively, 14–22, 12–17 and 9–15 ridges on the egg‐floats. The mode number of ridges among the eggs laid by individual females in these stocks was 16–19,13‐16 and 10–14, respectively. The category with the highest egg‐float ridge number corresponded with the type‐form and the lowest with var. mysorensis Sweet and Rao; the new egg‐float category with ridge number modes of thirteen to sixteen was designated as ‘intermediate’. All three forms, i.e. type‐form, intermediate and mysorensis were observed in semi‐urban areas while only intermediate and mysorensis were seen in rural areas. Breeding experiments indicated no post‐copulatory barriers between the populations. Likelihood analysis of the results of crosses and back crosses indicated that variation in ridge number is controlled by more than one genetic factor. The stocks with different ridge numbers are best considered as ‘ecological variants’.
Suppressive action of Samorin on the cyclical development of pathogenic trypanosomes in Glossina morsitans centralis
Authors: MOLOO S. K. , KAMUNYA G. W.
Published: March 2008

Male Glossina sexually sterilized by gamma‐irradiation are as efficient vectors of trypanosomiasis as fertile males. An attempt was made, using isometamidium chloride (Samorin), to interfere with the cyclical development of trypanosomes in sterile males, destined for use in the sterile insect release (SIR) method of tsetse eradication. The infection rate with mature Trypanosoma congolense Broden was effectively reduced in sterile male Glossina morsitans centralis Machado, when the flies were fed on an infected goat 2 days after they were fed as tenerals on an in vitro bloodmeal containing 8 μg Samorin/ml blood. The infection rates with mature T. vivax Ziemann and T. brucei brucei Plimmer & Bradford were completely suppressed at this drug dose. When sterile teneral males were fed on a bloodmeal containing 12 fig/m Samorin and given the infected bloodmeal 10 days later, infections by mature T. vivax, T. congolense and T.b.brucei were completely suppressed. Hence in the management of a tsetse eradication programme utilizing the SIR method, it is recommended that the sterile teneral male tsetse should, prior to release, be given a bloodmeal containing Samorin at 12–15 μg/ml blood. This will effectively suppress future disease transmission.
Field trial of the effectiveness of indoor‐spraying with pirimiphos‐methyl emulsion for malaria control in a tribal area of Phulbani district, Orissa State, India
Authors: DAS M. , SRIVASTAVA B. N. , RAO C. KRISHNA , THAPAR B. R. , SHARMA G. K.
Published: March 2008

Abstract. A field trial of malaria vector control was conducted in Phulbani district, Orissa, during 1984 and 1985. Indoor‐spraying of pirimiphos‐methyl emulsion formulation was undertaken at an application rate of 2 g/m2 in two sections (population 14,692) of Nuagaon Primary Health Centre. Houses in two adjacent sections (population 21,450) were sprayed with DDT a water dispersible powder (wdp) formulation at 1 g/m2 for comparison purposes. Operational problems in this area come from the tendency of tribal people to re‐plaster over wdp applications.

Pre‐spray malariological indices in the trial area were 38% slide positivity rate, 37% slide falciparum rate and 12.1% annual parasite incidence.

Densities of Anopheles annularis Van der Wulp, An.culicifacies Giles, An.fluviatilis Theobald and other potential malaria vectors were reduced in the pirimiphos‐methyl trial area 2–35‐fold more than in the area sprayed with DDT.

Malariological indices were reduced by 65–68% in the pirimiphos‐methyl sprayed area compared with only 26–35% reduction in the DDT sprayed area.

Spraymen and villagers experienced no adverse side‐effects from residual house‐spraying with pirimiphos‐methyl emulsion and it is concluded that this organophosphate product has advantages for malaria vector control, especially in operationally difficult situations.
Observations on the Anopheles gambiae complex in the Senegal River Basin, West Africa
Authors: PETRARCA V. , VERCRUYSSE J. , COLUZZI M.
Published: March 2008

Abstract. 1. Three sibling species of mosquitoes of the Anopheles gambiae complex are found in the Senegal River Basin: An.melas Theobald, An.gambiae Giles and An.arabiensis Patton.

2. An.melas is restricted to the river delta and environs where saltwater breeding places are present.

3. An.gambiae and An.arabiensis are sympatric in the study area; An.arabiensis predominates in coastal zones where it breeds also during the dry season; An.gambiae predominates in inland areas where breeding is mostly restricted to the rainy season (July‐September).

4. An.arabiensis is chromosomally polymorphic all over the study area, with much variation of inversion frequencies, particularly for the 2Ra arrangement.

5. An.gambiae is characterized by a very high frequency of the 2R6‐2La inversion arrangement which is typical of the Savanna chromosomal form.
The effect of Brugia pahangi infection on survival of susceptible and refractory species of the Aedes scutellaris complex
Authors: IBRAHIM M. S. , TRPIS M.
Published: March 2008

Abstract. . Life table statistics were used to examine the survival functions of filarial susceptible and refractory species of the Aedes scutellaris (Walker) group of mosquitoes, following infection with high and moderate doses of Brugia pahangi (Buckley & Edeson). Survivorship curves and hazard function curves were generated, and the median survival times and the proportions of mosquitoes surviving beyond the extrinsic incubation period of the parasite were determined.

In the susceptible populations of Aedes polynesiensis Marks, Ae.pseudo‐scutellaris (Theobald) and Ae. tabu Ramalingam & Belkin a dose‐response relationship was detected between parasite load and mortality. This relationship was characterized by a significant reduction in the proportions of infected female mosquitoes surviving at days 1 and 9 postinfection, reduction in the median survival times and an increase in the hazard rates as the infectious dose increased.

The survival of the refractory species, Ae.alcasidi Huang and Ae.katherinensis Woodhill was not significantly affected by the infection. A positive correlation between microfilaraemia in the vertebrate host and parasite load in the susceptible mosquito populations was also observed.

Regression analysis of the number of parasites recovered from susceptible mosquitoes at the time of death showed that mosquitoes at highest risk of dying harboured from 11.6 to 19.4 infective larvae when fed on a gerbil with sixty‐five microfilariae per 20,μl blood; this resulted in 34.4–40.2% mortality by day 9 postinfection. A mean number of 32.6–46.9 infective larvae was observed when these populations were exposed to a gerbil with a microfilaraemia of 150 mf/20 μl and resulted in 72.8% to 80% mortality in these populations. Viable infective larvae were recovered from infected mosquitoes up to 50 days postinfection.
An experimental assessment of the tampan tick Ornithodoros moubata as vector of hepatitis B virus
Authors: JUPP P. G. , JOUBERT J. J. , CORNEL A. J. , SWANEVELDER C. , PROZESKY O. W.
Published: March 2008

Abstract. Wild‐caught and colonized tampan ticks, Ornithodoros moubata (Murray), were fed on hepatitis B virus (HBV)‐positive blood‐means in a series of four experiments.

Hepatitis B surface antigen (HBsAg) persisted in nymphal and adult ticks for up to 779 days, while the epsmark antigen (HBeAg) persisted in mature nymphs up to 13 days, in adult males up to 11 days and in adult females up to 16 days. HBsAg was transmitted trans‐stadially through two moults during the life cycle but transovarial transmission did not occur. The surface antigen was transmitted by two out of fifteen single ticks into 0.4 ml aliquots of HBV‐negative blood, although six groups of ticks failed to transmit into 5.5 ml aliquots of blood: this antigen was not transmitted to hamsters. HBsAg was detected in samples of the ticks' coxal and rectal fluid secretions always at the infecting feed and usually at the second feed. HBeAg was only detected in one of two samples of coxal fluid collected at the infecting feed.

The results as a whole indicate that no biological multiplication of virus occurs in O.moubata but that mechanical transmission from ticks to man could occur by: (i) contamination of a person when crushing infected ticks; (ii) infection by bite; (iii) contamination with coxal fluid, especially by scratching bites. This is thought to take place among the Kavango tribe in their village huts in north‐eastern Namibia where infestations of infected O.moubata occur.
Reduced susceptibility to permethrin and its relationship to DDT resistance in larvae of Anopheles stephensi
Authors: MALCOLM C. A.
Published: March 2008

Abstract. Permethrin selection of DDT resistant Anopheles stephensi Liston mosquito larvae produced a reduction in susceptibility to knockdown (2 h exposure) of 17‐fold, but only 1.6‐fold to kill (24 h exposure). Genetic analysis, incorporating visible mutant markers, was interpreted as indicating that, through multigenic inheritance, several interacting genetic factors were collectively responsible for reduced larval susceptibility to knockdown. These were maintained together only under selection pressure, as the effect was lost quickly in the absence of selection or with outcrossing. The 30–40‐fold DDT‐resistance found in the parental strain was barely altered by permethrin selection, suggesting no relationship with the major source of DDT resistance. This was confirmed in single family studies. Some evidence for an additional tolerance to DDT was found to be associated with reduced larval susceptibility to permethrin.
Selective attractiveness of rodent‐baited traps for female blowflies
Authors: AVANCINI RITA M. P. , LINHARES ARíCIO X.
Published: March 2008

Abstract. Five species of Calliphoridae, mostly females, were collected using fly‐traps baited with freshly killed rodent carcasses. Female blowflies were examined to determine the stages of ovarian development.

The traps were selective for certain ovarian stages which varied according to the species. Phoenicia eximia (Wiedemann) was attracted to the traps mainly to oviposit, whereas females of Chrysornya albiceps (Wiedemann), C.putoria (Wiedemann) and C.megacephala (Fabricius) were captured in intermediate stages of oogenesis but seldom with eggs mature for oviposition.

It is concluded that this kind of baited trap is unsuitable for the collection of male blowflies and that samples of female blowflies are specifically biased in favour of certain ovarian conditions.
Anti‐mosquito antibodies decrease the reproductive capacity of Aedes aegypti
Authors: RAMASAMY MANTHRI S. , RAMASAMY RANJAN , KAY BRIAN H. , KIDSON CHEV
Published: March 2008

Abstract. Aedes aegypti (L.) fed on rabbits immunized with mosquito antigens showed a reduction in fecundity in the first oviposition and decreased viability of the progeny. Feeding behaviour of mosquitoes was not affected and no significant mortality was observed due to the presence of anti‐mosquito antibodies in the bloodmeal. Antibodies were detected in the oocytes of mosquitoes 48 h after the bloodmeal. The role of specific antibodies in influencing fecundity is discussed.
Evidence for a ‘memorized’ home range in Anopheles farauti females from Papua New Guinea
Authors: CHARLWOOD J. D. , GRAVES P. M. , MARSHALL T. F. de C.
Published: March 2008

Abstract. Evidence is presented that female Anopheles farauti Laveran released in an alien village dispersed more, in their first oviposition cycle after release, than females released in their village of capture. In a subsidiary experiment transporting the mosquitoes did not affect dispersal; wind speed or direction was not sufficient to account for the phenomenon. It is hypothesized that these permanent‐pool breeding mosquitoes make appetitive long‐range flights to oviposition sites. Mosquitoes blood‐fed before midnight had a shorter oviposition cycle than those fed just before dawn. Nulliparous females, and those with well‐defined ovariolar dilatations, predominated in the early evening whereas females that had oviposited recently were largely collected in the middle and later parts of the night.
DNA hybridizations on squash‐blotted sandflies to identify both Phlebotomus papatasi and infecting Leishmania major
Authors: READY PAUL D. , SMITH DEBORAH F. , KILLICK‐KENDRICK ROBERT
Published: March 2008

Abstract. Epidemiological field studies on leishmaniasis have been hampered by the laborious, and often inefficient, methods used to assess the rates of infection of sandfly vectors (Diptera; Phlebotominae) by species of the causative disease organisms, protozoal parasites of the genus Leishmania (Kinetoplastida; Trypanosomatidae). We report the rapid and accurate identification of both sandfly vector (Phlebotomus (Phlebotomus) papatasi (Scopoli)) and infecting Leishmania major Yakimov & Schokov by DNA hybridizations to squash‐blotted sandflies. Large numbers of whole (infected) sandflies can be quickly squashed on to nylon hybridization filters and (following standard procedures) the filter‐bound DNA can be hybridized sequentially to cloned, multicopy genomic sequences that are specific for species of Leishmania (kinetoplast DNA) or for the sandfly (ribosomal (r) DNA). Our sandfly probe consists of a 3.2 kb fragment of the intergenic ‘non‐transcribed’ spacer of rDNA of P.papatasi that we have detected only in this species: it is present in all six geographically isolated populations tested (from Tunisia through to India) but cannot be detected in the morphologically similar P. (Phlebotomus) duboscqi Neveu‐Lemaire, the vector of Leishmania major south of the Sahara; it also cannot be detected in Phlebotomus species of the subgenera Larroussius and Paraphlebotomus that together with P.papatasi are the dominant man‐biting sandflies in north African foci of zoonotic cutaneous leishmaniasis, where (as in many arid regions of western Asia) P.papatasi is believed to be the sole vector of L.major.
Effects of 'closed' houses on the Aedes aegypti eradication programme in Trinidad
Authors: CHADEE DAVE D.
Published: March 2008

Abstract. The effects of closed (i.e. locked) houses on the efficiency of control measures against Aedes aegypti (L.) were monitored weekly for 1 year (March 1981 to February 1982) using ovitraps in the towns of Felicity and Trincity, Trinidad. Regular anti‐aegypti activities comprised source reduction, focal treatment with larvicidal 1% temephos sand granules and perifocal treatment with 40% wp fenthion.

In Felicity, only 6% of houses were closed and after each treatment cycle ovitrap indices showed 100% control. In Trincity, 32% of houses were closed and after each treatment cycle reductions in ovitrap indices were less than 50%.

Ae.aegypti eggs sampled in ovitraps totalled 493 (1–70 per positive paddle) in Felicity and 2310 (1–75 per positive paddle) in Trincity; twenty‐three ovitraps were found to be positive in Felicity and 247 in Trincity.

Ae.aegypti was successfully eliminated from Felicity during weeks 40–52 using focal/perifocal treatment monitored by ovitraps. Control failure in Trincity was attributed to the survival of untreated Ae.aegypti populations in closed houses.

Recommendations to improve gaining access for inspection and treatment of closed houses include having control/surveillance workers commence activities at 06.00 hours on weekdays, to work at weekends or during school holidays, or as a last resort to invoke court orders against householders harbouring Ae.aegypti.
Panveld oviposition sites of floodwater Aedes mosquitoes and attempts to detect transovarial transmission of Rift Valley fever virus in South Africa
Authors: GARGAN THOMAS P. , JUPP PETER G. , NOVAK ROBERT J.
Published: March 2008

ABSTRACT. Floodwater aedine mosquito eggs were recovered from soil samples taken from grassland depressions, called pans, in the Orange Free State Province of South Africa. A sedge, Mariscus congestus (Vahl) C. B. C1., was a useful indicator of Aedes (Ochlerotatus) juppi Mcintosh oviposition areas. No transovarial transmission of virus was demonstrated by Ae. juppi females reared from the eggs and allowed to feed shortly after eclosion on hamsters. No virus was recovered from 557 pools of 5425 adult Ae. juppi that were collected as eggs and reared to the adult stage in the laboratory. Rift Valley fever virus replicated to high titres in experimentally infected Ae. juppi females, but horizontal transmission experiments proved inconclusive.
The distribution of phlebotomine sandflies in the principal ecological zones of Jordan
Authors: LANE R. P. , ABDEL‐HAFEZ S. , KAMHAWI S.
Published: March 2008

ABSTRACT. . A survey of the sandflies (Diptera: Psychodidae) of Jordan increased the number of species known from the country from three to thirteen. Composition of the phlebotomine fauna and the relative abundance of sandfly species differ among the six climatic zones, with a general distinction between the dry desert zones and the more humid Mediterranean zones. Species of Phlebotomus predominate in the former and Sergentomyia in the latter. Within the desert zone some species are restricted to the eastern desert and others to the Jordan Valley in the west.
ELISA absorbance cut‐off method affects malaria sporozoite rate determination in wild Afrotropical Anopheles
Authors: BEIER JOHN C. , ASIAGO CHARLES M. , ONYANGO FRED K. , KOROS JOSEPH K.
Published: March 2008

ABSTRACT. Malaria sporozoite infection rates in a mixed species group of 244 Anopheles gambiae Giles sensu lato and 115 An. funestus Giles wild female mosquitoes were compared using three methods to determine cutoff absorbance values for positivity of a Plasmodium falciparum Welch enzyme‐linked immunosorbent assay (ELISA). Positive controls were based on P. falciparum circumsporozoite protein. As negative controls, four wild male Anopheles were included on each microtitre plate; tests were repeated on four consecutive days for each plate.

Infection rates were estimated at 13.1–22.8% using the mean absorbance value of negative controls plus three standard deviations, 11.7–12.8% using double the mean and 12.5–13.6% using the fixed cut‐off value of 0.20 (allowing for 20% variation in negative control absorbance values).

Observed agreement for positivity or negativity among samples tested four times was 98.6% for the 2× mean method, 97.2% for the fixed cut‐off 0.20 value, but only 82.7% for the mean +3 SD method. It was concluded that the 2× mean cut‐off method is most reliable for field studies. P. falciparum sporozoite rates of 12.2% in An. funestus and 11.9% in An. gambiae s. l. were thus determined on the basis of the 2× mean cut‐off method.

This comparative evaluation demonstrates that vector infectivity rates can be seriously over‐estimated from sporozoite ELISA tests, by as much as 87% in one case considered here, depending on the absorbance cut‐off method applied for negative controls.
Production of a hybrid between the bedbugs Cimex hemipterus and Cimex lectularius
Authors: NEWBERRY K.
Published: March 2008

ABSTRACT. Of 479 eggs laid by female Cimex lectularius Linnaeus and C. hemipterus (Fabricius) mated by males of the other species, one was fertile and gave rise to a first stage nymph. The egg showed sculpturing typical of C. hemipterus, the female parent, and the nymph conformed to the narrow pronotum and abdomen of this species, being significantly different from C. lectularius in the width of the abdomen. Because the orientation and lengths of the bristles on the sides of the abdomen were distinctly different from C. hemipterus and closely resembled C. lectularius, the single nymph obtained from the cross C. hemipterus xlectularius was interpreted as being a hybrid rather than a product of parthenogenesis.
Pathological effects of Blastocrithidia triatomae (Trypanosomatidae) on the reduviid bugs Triatoma sordida, T. pallidipennis and Dipetalogaster maxima after coprophagic infection
Authors: SCHAUB G. A. , BREGER BEATE
Published: March 2008

ABSTRACT.Developmental time and mortality in nymphs of the reduviid bugsTriatoma sordida(Stål),Triatoma pallidipennis(Stål) andDipetalogaster maxima(Uhler) were studied in uninfected groups and in those infected withBlastocrithidia triatomaeCerisolaet al.(Trypanosomatidae). InT. sordidaandT. pallidipennis, major vectors of Chagas' disease in Brazil and Mexico respectively, infection withB. triatomaewas associated with slight developmental retardations in the final instars, and increased mortality in the pre‐adult instar. These effects were less evident inT. pallidipennis, but in this species a total infection rate of only 5–15% was achieved, compared with about 45% inT. sordida.In contrast,D. maximawas strongly affected byB. triatomae:nymphal development was retarded and complete mortality occurred in some groups exposed to infection, although not all bugs were infected.
Serologic diagnosis of Oestrus ovis (Diptera: Oestridae) in naturally infested sheep
Authors: BAUTISTA‐GARFIAS CARLOS R. , ANGULO‐CONTRERAS ROSA M. , GARAY‐GARZON ENRIQUE
Published: March 2008

ABSTRACT. Sera from eighteen control sheep supposed to be free from parasitism by Oestrus ovis Linnaeus, 1761, and from 100 sheep raised in an enzootic area of O. ovis infestations were tested to detect anti‐Oestrus antibodies by double immunodiffusion (DD) and indirect haemagglutination (IH) tests with somatic crude antigens from first (L1), second (L2) and third (L3) instar of O. ovis larvae. At necropsy, eighty‐eight out of 100 sheep from the O. ovis infested area were found to be parasitized while the eighteen control ovines did not show Oestrus larvae. Examination of the sera from the parasitized sheep by DD showed positive results of 42% for L1, 59% for L2 and 18% for L3. Screening the sera with IH gave sensitivities of 100% for LI, 100% for L2 and 97.7% for L3. Sheep, naturally parasitized by gastrointestinal nematodes, presented no cross immune reactions in DD tests with the three larval stages of O. ovis or with L2 larvae in IH tests.
Factors influencing silhouette trap captures of the blackfly Austrosimulium bancrofti in Queensland, Australia
Authors: BALLARD J. W. O. , BARNES A.
Published: March 2008

ABSTRACT. Three silhouette traps of novel design were used to investigate the trap finding ability of female Austrosimulium bancrofti (Taylor) (Diptera: Simuliidae) in southeast Queensland. The traps were ‘upright’, ‘elongate’ or ‘square’ in shape. Five highly significant factors: hour after sunrise, temperature, relative humidity, trap shape and distance between traps, were included in a model which generated fitted estimates of flies captured under defined conditions. The rate of increase and the level of maximum capture rate indicated that the elongate trap captured the highest numbers of blackflies. An interaction between hour after sunrise and temperature suggests a strong endogenous modification of trap finding activity. Numbers captured increased with increasing distance between traps and decreasing relative humidity. The importance of these results in understanding behaviour of A. bancrofti is discussed.
Effects of screen materials on droplet size frequency distribution of aerosols entering sentinel mosquito exposure tubes*
Authors: BOOBAR L. R. , DOBSON S. E. , PERICH M. J. , DARBY W. M. , NELSON J. H.
Published: March 2008

ABSTRACT. Aerosol filtration effects of three types of mesh screen used for mosquito cages were evaluated with aerosolized water, mineral oil and chlorpyrifos. The screen materials were two nylon tulles (3times4 and 8times11 repeats per cm2) and corrosion‐resistant steel (7times7 repeats per cm2). Open areas of these three mesh materials were, respectively, 94%, 79% and 88%.

Aerosol droplet size frequency distributions were altered when passed through test screens of these materials fitted to standard tubes from World Health Organization test‐kits for exposure of adult mosquitoes. The alterations included reductions in total droplets and volume median diameter (VmD). Nylon screen with fewer repeats of the mesh altered droplet VmD and frequency distribution the least, allowing the greatest number of droplets to enter sentinel mosquito cages for bioassays of mortality‐rates.

The greater filtration effect of screens with less open area, giving rise to selective deposition of particular droplet sizes on the screen material, could result in anomalous exposures of test mosquitoes to contact with insecticide filtrate on the screen substrate. This might help to explain the poor correlation often observed between insecticide aerosol impact on wild target mosquito populations as compared with sentinel caged mosquitoes. In addition to other standard test procedures, the need for standardization of materials used for construction of sentinel cages employed for aerosol bioassays is emphasized.
Effects of salinity on the larvae of some Afrotropical anopheline mosquitoes
Authors: COETZEE MAUREEN , SUEUR DAVID LE
Published: March 2008

ABSTRACT. Laboratory experiments showed that the larvae of some freshwater‐breeding Afrotropical anopheline species exhibit various degrees of tolerance to 25% sea‐water. At 24oC, survival rates from egg to fourth instar larva were significantly less in salt‐water than in freshwater for four species: 39.5% versus 55.4% for Anopheles tenebrosus Dönitz, 31.9% versus 86.2% for An. mousinhoi De Meillon & Pereira, 3.5% versus 67.9% for An. pharoensis Theobald and 3.9% versus 41.9% for An. quadriannulatus (Theobald). Conversely, An. merus Dönitz showed a significantly better survival rate of 46.4% in 25% sea‐water compared with 15.5% in freshwater. Simulated winter conditions did not significantly change these differential survival rates of An. merus. Effects of salinity on the anal papillae of third instar larvae are discussed.
Laboratory response of female Lutzomyia longipalpis sandflies to a host and male pheromone source over distance
Authors: MORTON I. E. , WARD R. D.
Published: March 2008

ABSTRACT. A nylon net cage (260×40×40 cm) provided with unidirectional air flow was used to demonstrate the response of female sandflies, Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) to a host and extract of male pheromone glands over a distance of 240 cm. Females responded more rapidly and in greater numbers to the host if male pheromone was present. Results suggest that one function of the pheromone may be to attract females from some distance to a common mating site, on or near the host.
A laboratory investigation of mosquito larval predation by Toxorhynchites moctezuma on Aedes aegypti
Authors: SHERRATT THOMAS N. , TIKASINGH ELISHA S.
Published: March 2008

ABSTRACT. 1. Functional responses of predatory Toxorhynchites moctezuma (Dyar & Knab) larvae feeding on Aedes aegypti (L.) larvae (Diptera: Culicidae) were found to be type II of Holling (1959) and Rogers (1972).

2. Estimates of searching rate were generally higher for later instar predators. The search rate of second instar predators declined as prey instar increased, but fourth instar Tx. moctezuma had the highest search rate for second instar Ae. aegypti.

3. Prey handling times were higher for early instar predators and late instar prey.

4. When presented with mixtures of two instars of Ae. aegypti, second instar Tx. moctezuma showed frequency independent selectivity for the early instars, whereas fourth instar predators showed frequency independent selectivity for the late instars of Ae. aegypti. There was no evidence of frequency dependent predation. Preferences appeared to be transitive.

5. Extended random predator equations, using parameters derived from the functional responses, did not adequately describe the outcome of predation in the prey mixture experiment, even when the possibility of optimal switching behaviour was accounted for.
Ovarian development in the blowflies Chrysomyaputoria and C. megacephala on natural diets
Authors: LINHARES A. X. , AVANCINI R. P. M.
Published: March 2008

ABSTRACT. Fresh human,‐chicken and cattle faeces were compared as diets for adult female blowflies Chrysomya megacephala (Fabricius) and C. putoria (Wiedemann) (Diptera: Calliphoridae). As controls, sugar and raw beef liver were used. For females of both species, fresh beef liver was the best of these diets: oogenesis was completed in 10–13 days. Human or chicken faeces facilitated slower oogenesis in 27–48 days. On a diet of cattle faeces, C. putoria females began vitellogenesis only 17 days after emergence, whereas females of C. megacephala remained previtellogenic until the end of the experiment (56 days).
Vertical transmission of hepatitis B virus in Culex quinquefasciatus
Authors: FOUCHÉ ALIDA , CREWE R. M. , WINDSOR I. M.
Published: March 2008

ABSTRACT. An investigation of the vertical transmission of hepatitis B virus (HBV) in Culex quinquefasciatus Say revealed the presence of low levels of the virus in adult Fi progeny from the first ovarian cycle of mosquitoes infected by feeding on HBV positive human blood. HBV was not transmitted vertically during the second, third and fourth ovarian cycles nor to the F2 generation. The salivary glands, ovaries and faeces of the Fj generation did not contain detectable levels of HBV. Progeny of female Cx quinquefasciatus mated with F1 males were negative for HBV.
Scanning electron microscopy of the posterior spiracles of cattle grubs Hypoderma bovis and Hypoderma lineatum
Authors: COLWELL DOUGLAS D.
Published: March 2008

ABSTRACT. Posterior spiracles of newly hatched first instar larvae of Hypoderma bovis (L.) and H. lineatum (DeVill.) consist of two pairs of spiracular openings. Each pair is surrounded by a rima bearing three spines. Posterior spiracles of second instar larvae are composed of a pair of medial ecdysial scars bounded laterally by spiracular plates. H. bovis spiracular plates have twenty‐nine to forty openings, each surrounded by a slightly raised rima. H. lineatum spiracular plates have eighteen to twenty‐five openings. Spiracular openings lead to posterior felt chambers which are connected to a common anterior felt chamber filled with a meshlike network. In third instar H. bovis each medial ecdysial scar is surrounded by a strongly concave spiracular plate. Spiracular openings are surrounded by slightly raised rima. Most rimae bear a spine. Spiracular plates of H. lineatum are flat and rimae are without spines. Each spiracular opening leads to a posterior felt chamber, several of which are confluent with a larger anterior felt chamber. Anterior felt chambers open into the dorsal longitudinal tracheal trunk. Felt chambers in third instar larvae are also filled with a complex mesh.
Genetic variation in the body weight of ticks of the Rhipicephalus appendiculatus/zambeziensis complex
Authors: WOUTERS G. , BERKVENS D. , GOMES A. F.
Published: March 2008

ABSTRACT. Sixteen strains of ticks of the Rhipicephalus appendiculatusl zambeziensis complex were created by cross‐breeding for one to three generations. The body‐weights of adult male ticks of these consanguineous lines were compared. A significant genetic variation was distinguished between the groups. Three classes whose mean weights varied around, respectively, 2, 3 and 4 mg/adult male tick, were found. This variation in weight may be explained by hybridization between R. appendiculatus Neumann and R. zambeziensis Walker, Norval & Corwin. Hybrid ticks were undersized whereas R. appendiculatus and R. zambeziensis gou'ps had significantly higher weights.
Genetic transformation of the mosquito Aedes aegypti by micro‐injection of DNA
Authors: MORRIS ALISON C. , EGGLESTON PAUL , CRAMPTON JULIAN M.
Published: March 2008

ABSTRACT. We report the successful introduction of heterologous DNA sequences into embryos of the mosquito Aedes aegypti (L.) by microinjection. The injected DNA carrried P transposable element sequences, derived from and known to facilitate transformation in Drosophila melanogaster. Two plasmids, one of which carried a dominant selectable marker, were introduced into the posterior of embryos prior to pole cell formation and subsequently taken up into the germ line of transformed individuals. Stable transfer of the selectable marker (G418 resistance) was demonstrated over two generations. The precise nature of these putative P mediated integration events is currently being investigated. However, the results presented here establish the technique of DNA transformation for the genetic manipulation of Aedes aegypti.
Rapid microtitre plate test distinguishes insecticide resistant acetylcholinesterase genotypes in the mosquitoes Anopheles albimanus, An.nigerrimus and Culex pipiens
Authors: FFRENCH‐CONSTANT R. H. , BONNING B. C.
Published: March 2008

ABSTRACT. A rapid method of distinguishing insecticide insensitive acetylcholinesterase (AChE) genotypes was applied to three species of mosquitoes. This relies on comparing rates of an AChE mediated reaction in the presence and absence of insecticides which are inhibitors, using a kinetic microtitre plate reader. Clearer and more rapid resolution between genotypes was achieved than with previous assays which measure the amount of product formed at a fixed end‐point. Results are presented for the Fls from crossing resistant and susceptible Anopheles albimanus Wiedemann and Culex pipiens L., for a strain of An.albimanus with a translocation linking the AChE gene to the Y chromosome and for field collected An.nigerrimus Giles. Propoxur and malaoxon were used as inhibitors. In all three species the enzyme was more insensitive to propoxur than malaoxon. Susceptible enzymes in all species also showed higher uninhibited AChE activity than their resistant counterparts. Presentation of both inhibited and uninhibited activities side by side may be useful to identify insects likely to be misclassified due to abnormally low AChE activities. Estimated frequencies of the three resistance genotypes in field populations of An.nigerrimus conformed to Hardy‐Weinberg ratios. The implications of this technique for laboratory and field studies on insects are discussed.
Seasonal patterns of rodents, fleas and plague status in the Western Usambara Mountains, Tanzania
Authors: NJUNWA K. J. , MWAIKO G. L. , KILONZO B. S. , MHINA J. I. K.
Published: March 2008

ABSTRACT. Field and commensal rodents were live‐trapped at three villages in an active focus of plague (Yersinia pseudotuberculosis pestis) in Lushoto District, Western Usambara Mountains, Tanga Region, Tanzania, from December 1983 to November 1984. Their flea ectoparasites were collected, identified and counted. The rodent carcasses were serologically examined for specific plague antibodies and antigens, and bacteriologically examined for bipolar staining bacilli.

A total of 1758 traps were set during the 12‐month period and 924 animals were caught. From these, 1037 fleas were collected. Rattus rattus (L.), Praomys natalensis (Smith) and Lophuromys flavopunctatus Thomas comprised the largest proportions of the rodent population, while Dino‐psyllus lypusus Jordan & Rothschild, Ctenophthalmus calceatus Waterston and Xenopsylla brasiliensis (Baker) were the dominant flea species.

Rodents were most abundantly trapped during December and January. Flea indices were highest from December to May. Human plague was most active from November to March. Rodents contained plague antibodies every month except May and July, with a peak in September. Plague antigens and bipolar bacilli were detected in rodent organs during January‐April. From the product of abundance and infection rate, the most prevalent rodent hosts of plague appeared to be R. rattus, Otomys ango‐niensis Wroughton, P.natalensis and Pelomys fallax (Peters).

Continuous integrated control of rodents and fleas was recommended, reinforced by quarantine and maintenance of a surveillance service for clinical detection, diagnosis and treatment of patients in the plague endemic area.
Response of insecticide‐resistant and susceptible houseflies (Musca domestica) to a commercial granular bait formulation containing methomyl
Authors: BARSON GRAHAM
Published: March 2008

ABSTRACT. Female houseflies (Musca domestica L.) from a susceptible and a multi‐insecticide‐resistant strain were used to evaluate the relative toxicity of an insecticide bait formulation of the carbamate insecticide methomyl. Individual flies were allowed to feed on bait granules for an unrestricted period or for 5 s. Resistant flies took longer than susceptible flies to initiate a feeding response. When allowed to feed continuously, those from the resistant strain spent longer feeding than susceptible ones. The time taken to knock‐down (KD), including feeding times, was significantly greater for resistant than susceptible flies (P<0.001), but once the proboscis was withdrawn from the granule there was no difference in KD times between the strains. All flies from both strains were knocked down, and only a very small number of resistant and susceptible flies recovered. The toxic effects of methomyl on flies which were restricted to a 5 s feed ranged from no observed effect to KD in <1 min. After feeding for 5 s, 81 % of resistant and 98% of susceptible flies developed signs of methomyl poisoning. More resistant than susceptible flies recovered from KD, giving final mortalities of 46% and 88% respectively. With both feeding regimes, some flies of both strains which had apparently recovered from KD had lost their ability to fly. Observations have also shown that 8% of resistant flies may have been repelled by methomyl granules. The implication of these results on the survival of M. domestica in intensive animal units following exposure to methomyl bait is also discussed.
Selection of Anopheles stephensi for refractoriness and susceptibility to Plasmodium falciparum
Authors: FELDMANN A. M. , PONNUDURAI T.
Published: March 2008

ABSTRACT. Variation in susceptibility of the vector Anopheles stephensi Liston to the human malaria parasite Plasmodium falciparum (Welch) was demonstrated using twelve strains of mosquitoes and one strain of parasites cultured in vitro.

The Beech strain of An. stephensi exhibited greatest natural refractoriness, but with high intrapopulation variability. By selection for the required characteristic, two refractory lines of the Punjab strain and one highly susceptible line of the Sind strain were obtained. The median number of oocysts in the two refractory lines was less than 4% of that in the unselected line, whilst the highly susceptible line yielded about twice as many oocysts as the unselected line.

Selection progressed more by keeping the descendants of individual females separate and selecting between them (individual selection) rather than pooling the progeny of all selected mosquitoes (mass selection). Using the former procedure many lines were lost due to inbreeding depression, but the outcome was more successful.
Assessment of a silhouette trap for sampling zoophilic blackflies (Diptera: Simuliidae)
Authors: McCALL P. J. , TREES A. J.
Published: March 2008

ABSTRACT. A collapsible animal‐type silhouette trap was designed to catch zoophilic female blackflies (Diptera: Simuliidae) which feed on the head or ventral surface of cattle. The trap was assessed for its ability to sample attacking blackflies by comparison with simultaneous manual catches from a bait cow, in an enzootic bovine onchocerciasis area in North Wales. In thirteen 1‐hour collections, the trap provided a representative sample of the blackfly population in terms of the relative abundance of species. There was a strong correlation between the catch sizes from both methods (r=+0.73), and the body site feeding preferences for all species were similar with both trap and cow. There was no significant difference between the Onchocerca spp. infection rates of flies caught by either method.
Long‐term storage of eggs of Simulium ornatum
Authors: GOLL P. H. , DUNCAN J. , BROWN N.
Published: March 2008

ABSTRACT. A method for the storage of non‐diapausing eggs of Simulium ornatum Meigen has been developed. High survival rates for 5–6 months depend on the age of eggs when placed at reduced temperature. A period of precooling or conditioning is required for 28 days before storage of the eggs at 1oC with lowering of oxygen partial pressure. Induced quiescence does not appear to affect development from egg to adult.
Bluetongue epidemiology in the Caribbean region: serological and entomological findings from a pilot sentinel system in Trinidad and Tobago
Authors: GREINER E. C. , ALEXANDER F. C. M. , ROACH J. , BORDE G. , TAYLOR W. P. , DICKINSON J. , GIBBS E. P. J.
Published: March 2008

ABSTRACT. When monitored by the agar gel immunodiffusion test for antibody to bluetongue viruses, a sentinel flock of twenty‐five lambs remained seropositive through the year, whereas in a sentinel herd of twenty calves only two individuals seroconverted and these became negative again within 2 months. A light trap operated with the calf herd yielded high numbers of Culicoides insignis Lutz (over 18,000 per trap night) along with C.filariferus Hoffman, C.pusillus Lutz, C.leopoldi Ortiz, C.foxi Ortiz, C.limai Barretto, C.diabolicus Hoffman and C.guyanensis Floch and Abonnenc. Culicoides were trapped at the sheep station which had housed the lambs 3 years following the sentinel study. No virus was isolated from pools of C.insignis, C.filariferus and C.pusillus. Six other species were collected in insufficient numbers to warrant attempted virus isolations.
Absence of outer caudal setae on all larval instars of Phlebotomus tobbi from the Ionian Greek islands
Authors: KILLICK‐KENDRICK R. , KILLICK‐KENDRICK M. , LEGER N. , PESSON B. , MADULO‐LEBLOND G. , PAGE A. M.
Published: March 2008

ABSTRACT. . Larval instars 2, 3 and 4 of Phlebotomus tobbi Adler, Theodor & Lourie from the Greek islands of Corfu and Zakynthos were found to have two caudal setae instead of the four usually present on these instars of Phlebotomus larvae. In a scanning electron microscope comparison with larvae of P.papatasi (Scopoli), a sensillum was seen in place of each outer seta of P. tobbi larvae, suggesting secondary loss of the setae. As the larvae of less than a tenth of the species and subspecies of the genus Phlebotomus have been seen and described, it cannot be assumed that those of P. tobbi are unique in having only two caudal setae. However, four caudal setae in late instars can no longer be considered as a constant character of the genus Phlebotomus. Observations on the larvae of P. tobbi also raise the question of the unknown function of the caudal setae.
The influence of seasonal temperatures on the natural regulation of the screw worm, Cochliomyia hominivorax, in the southern U.S.A.
Authors: READSHAW J. L.
Published: March 2008

ABSTRACT. The incidence of screwworm cases in Texas during the 1962‐82 sterile‐male eradication campaign is analysed in relation to seasonal temperatures and screwworm density. The analysis shows that screwworm outbreaks occur in response to favourable seasonal conditions, especially warm winters and cool summers. The outbreaks collapse following cold winters and hot summers. Screwworm density in autumn also influences rates of increase, possibly through a shortage of wounded hosts in the autumn‐winter period. The analysis provides a simple predictive model which not only accounts for the fluctuations in case incidence seen in Texas during the eradication campaign, which others have attributed to strain problems and release methods, but also simulates the historical pattern of screwworm abundance in both Texas and Florida over the last 100 years. It is concluded that screwworm, being essentially a tropical species, might well have been eradicated from the southern U.S.A. by exceptionally unfavourable climate such as occurred in Florida in 1958 and in Texas in the late 1970s and early 1980s. Certainly, unfavourable climate must have been important to the success of the eradication campaigns.
Monitoring tsetse fly populations. I. The intrinsic variability of trap catches of Glossina pallidipes at Nguruman, Kenya
Authors: WILLIAMS BRIAN , DRANSFIELD ROBERT , BRIGHTWELL ROBERT
Published: March 2008

ABSTRACT. During 1986 the tsetse fly Glossina pallidipes Austen was monitored daily at Nguruman, southwestern Kenya, using three unbaited biconical traps. This was done to investigate the nature and causes of daily variation in trap catches. The variability of the observed catches was compared to a model which includes the trapping probability and the stochastic variation in the sex‐ratio. By comparing the catches of male and female flies we are able to establish the sampling distribution of the trap catches. In addition to seasonal changes in the trap catches, day‐to‐day variations are observed and these are considered greater than the variation arising from the stochastic nature of the sampling process. Recommendations are made in relation to sampling tsetse fly populations.
Estimation of rates of predation on tsetse
Authors: ROGERS DAVID J. , RANDOLPH SARAH E.
Published: March 2008

ABSTRACT. The levels of natural predation of puparial and adult tsetse flies, Glossina pallidipes Austen, were investigated at Nguruman, Kenya, during January 1989. Puparial experiments involved the production, by individually tubed female flies, of naturally deposited, unhandled puparia in soil cores; handled puparia were obtained from groups of caged flies kept in the normal way. Equal numbers of handled and unhandled puparia were planted out at different densities (1, 2, 4 or 8 per linear metre) in fifty‐one natural puparial sites in four major vegetation types. After 10 days puparia were recovered using a soil corer and sieving system. Average predation rates (adjusted for the displacement of puparia by vertebrate activity at the puparial sites) were 9.4% and 7.8% for the two types of puparia during the experiment, equivalent to an average loss of 23.7% of all puparia during a normal 30‐day developmental period.

Maximum potential predation rates of adult flies were investigated by pinning freshly killed adults at densities of1, 2, 4 or 8 per m3 to natural vegetation and scoring the results after 24 h. 70% of flies were attacked during this time, by a variety of predators, thought to include both vertebrates and invertebrates.

No density dependence was detected in the experiments, either because natural puparial densities were too low for it to occur at this stage of the life cycle or because adult predation levels were too high for it to be detected.

Present results are compared and contrasted with previous results for this and another species of tsetse. Calculations of the life‐time fertilities of female tsetse suggest that the levels of puparial predation revealed by the present experiments are entirely realistic. Behaviour of the adult flies allows them to escape most of the considerable predation pressure under which they live. How they do so remains a mystery.
Age determination of Aedes cantans using the ovarian oil injection technique
Authors: HOC T. Q. , CHARLWOOD J. D.
Published: March 2008

ABSTRACT. A study of the age structure of a population of adult female Aedes cantans Meigen was undertaken using the ovarian oil injection technique to determine parity. Results showed that, contrary to popular opinion, ovariolar sacs do not form gonotrophic dilatations and cannot be used for physiological age determination. Dilatations were formed only by follicles which degenerate at a very early stage in the gonotrophic cycle. The proportion which consistently do degenerate (the gonotrophic diagnostic index) decreases in each successive cycle. Results showed that the mean age of the population during the study was 2.04 parous, which was one gonotrophic cycle less than expected, possibly due to scarcity of hosts in the area.