Recovery of Dictyocaulus species from the lungs of a Kashmir red deer (Cervus elaphus hanglu)

Dictyocaulus species infection has been reported in wild ruminants in Europe and New Zealand in areas where intensive deer farming is carried out (Corrigall and others 1980, Johnson and others 2003). Cattle are the primary host for Dictyocaulus viviparus, while cervids are the primary host for Dictyocaulus eckerti. D viviparus has also been recovered from deer and found to cause parasitic bronchitis. Although the adults and larvae recovered from deer were morphologically similar to D viviparus from cattle, the cervid isolates were thought to be a variant strain from their cattle counterpart (Corrigall and others 1988). This short communication describes the recovery of mature Dictyocaulus species lungworms at postmortem examination of a female gravid Kashmir red deer or hangul (Cervus elaphus hanglu) that had died of prolonged dystocia in the Dachigam National Park, Kashmir, India. The hangul is the only species of deer in the Indian sub-continent related to the European red deer (Cervus elaphus), in which Dictyocaulus species infection is a common occurrence. Postmortem examination was conducted on a recently captured adult, gravid female hangul in the Dachigam National Park, in May 2003. The deer had been rehabilitated from the Kangan area, which is situated within the same mountain range as Dachigam, after being rescued from the Sindh River. During the postmortem examination, the trachea was cut open from the pharynx downwards using a pair of blunt scissors, and lungworms were revealed in the froth in the trachea (Fig 1). Clinically, the deer had shown no distinctive clinical signs of lungworm infection except for mild respiratory distress in the terminal stage. Grossly, the lungs revealed mottling, with occasional areas of consolidation in the diaphragmatic lobes. Patchy areas of emphysema and atelectasis were observed on the surface of the lungs. The trachea showed congestion and profuse mucinous froth, from which six adult lungworms were recovered (Fig 1). No worms were detected in the terminal bronchioles. The worms were recovered and placed in formal saline solution for further examination. Their total body length was measured using a mm scale, and the worms were prepared with lactophenol for microscopic and micrometric studies. The shape of their buccal capsule wall was noted and its thickness calculated as described by Divina and others (2000). The dimension of eggs and, where present, the larvae contained inside them, was also measured. An ocular micrometer scale standardised to a stage micrometer scale (for each objective magnification) was used to measure the buccal cavity wall, egg and larvae dimensions under the microscope. Detailed examination of the worms revealed that they were all female and that their body length ranged from 2·5 to 3·0 cm. The worms were white and slender, and the intestine showed as a dark line. The buccal capsule was triangular in shape and very shallow, with four very small lips. The buccal capsule wall thickness was approximately 10 μm at its broadest end, while its length was approximately 20 μm. The vulva was situated behind the middle of the body. The uterus contained numerous embryonated eggs containing occasional first-stage larvae. The eggs measured approximately 110 x 40 μm and the larvae were up to 0·21 mm long. On the basis of their morphological features the worms were considered to closely resemble D viviparus, the common lungworm of cattle. To the authors’ knowledge, this is the first report of Dictyocaulus species infection in a hangul, and indicates that this species, which is perhaps the most endangered red deer species in the world (Gruisen 2001), is vulnerable to lungworm infection. Although respiratory distress was observed during the animal’s brief period of captivity, frank clinical signs of infection or paroxysmal coughing characteristic of the disease was not noted. The parasitic load was probably too small, when compared with other natural infections, to cause many significant pathological alterations or clinical signs. Signs of clinical disease are stated to be dependent on the parasitic load and the general health of the animal (Corrigall and others 1980). The presence of froth in the airways is attributed to irritation caused by the parasite, and the worms themselves feed on these exudates, which are abundant with inflammatory cells, particularly eosinophils. In the present case, the worms closely resembled D viviparus morphologically. Characteristics such as the buccal capsule wall thickness and length, total body length and total spicular length have been reported to have a positive correlation between various Dictyocaulus species, and so can be used to distinguish between species. Since all the parasites recovered were females, the spicular length could not be calculated. The total body length and buccal capsule wall thickness were within the ranges described for D viviparus in cattle by Divina and others (2000). However, it must be emphasised that the body length is related to the age of the worms, and cannot therefore be considered as a definitive parameter for identification, especially for young or immature parasites. Cross-infection by Dictyocaulus species between cattle and red deer has been established (Johnson and others 2003), but the lungs of red deer react relatively mildly to D viviparus infection in comparison to the reaction in cattle (Corrigall and others 1982). It therefore appears that there is a difference between D viviparus prevalent in both species. A ‘biological concept’ in this regard was proposed by Boev (1963), whereas Presidente and Knapp (1973) postulated that there had been an evolution of distinct physiological strains, well adapted to their natural hosts; antigenic differences have been indicated by Presidente and others (1972), while Enigk and Hilderbrandt (1965) suggested the existence of strains of D viviparus of different pathogenicity. Veterinary Record (2005) 157, 591-592