Cowdriosis (heartwater) in a Ugandan goat: a case report

M. K. Saimo, BVM, MSc, E. S. Bizimenyera, BVM, MSc, A. Mugisha, BVM, MSc, P. Nsamba, BVM, MSc, Department of Veterinary Medicine, J. B. Okuni, BVM, MSc, Department of Veterinary Pathology, Makerere University, PO Box 7062, Kampala, Uganda COWDRIOSIS (heartwater) is an infectious, non-contagious rickettsial tickborne disease of ruminants, characterised by high fever, hydropericardium and nervous signs. It is common in areas inhabited by its vectors, the ticks of the genus Amblyomma. The disease was first described in sheep in South Africa, in 1838. The causative agent was initially identified as Rickettsia ruminantium (Cowdry 1925a, b) but later renamed Cowdria ruminantium in 1953. Although cowdriosis was first reported in Uganda early last century (Lewis 1939), information on this disease has since been limited to unconfirmed, Veterinary Department Annual Reports (Anon 1990 to 1998). The tick vectors Amblyomma variegatum, Amblyomma gemma and Amblyomma lepedum are abundant throughout Uganda (Mathysse and Colbo 1987) and heartwater is therefore presumed to be endemic in most parts of Uganda (Mutugi and others 1995). The importance of this disease is often underestimated mainly due to difficulties in diagnosis (Uilenberg 1983) and in Uganda the problem is further complicated by the presence of other tickborne diseases, such as theileriosis, anaplasmosis and babesiosis. This short communication presents a case of cowdriosis which occurred in a goat in a herd kept at the Faculty of Veterinary Medicine, Makerere University, Kampala. A small herd of 14 cattle and 10 goats of mixed breeds are kept at the Faculty and are used for teaching purposes. The acaricide being used for tick control was amitraz (Taktic; Hoechst Roussel). Due to a lack of acaricides, however, the stockmen had neglected to spray the goats for some time, concentrating acaricide use on the cattle. There is known to be a heavy tick challenge in the area surrounding the faculty. A female Toggenberg-Mubende cross goat, approximately one year old and weighing 25 kg presented clinical symptoms of high fever (41.7°C), a stiff uncoordinated gait, and rapid loss of condition including anorexia, lethargy, depression and a rough coat. In spite of intramuscular injections with 3 ml of oxytetracycline 10 per cent (Duocycline; Univet), 4 ml multivitamins (Norbrook Labs), the goat became laterally recumbent the following day. There was ruminal stasis, mucopurulent nasal discharge and twitching of muscles. The above injections were repeated daily for three consecutive days, after which the goat became moribund with a subnormal temperature of 37-2°C. It was euthanased and submitted to the pathologist for postmortem examination. The findings of the postmortem examination were general cachexia, serous atrophy of body fat depots, widespread ecchymotic and'paint brush' haemorrhages in both the subcutis and viscera, with evidence of unclotted blood in veins. Hydropericardium with watery opalescent pericardial fluid was found. The mycocardium, as with all the skeletal musculature, was flabby. Kidneys were congested, with the right kidney being markedly enlarged. The spleen, lymph nodes and gall bladder were severely enlarged and oedematous. The brain had pinpoint haemorrhages in the parenchyma, a smear of the brain revealed elementary bodies in the capillary endothelium. The goat had an A variegatum tick in the interdigital space of the right fore leg but the tick was not tested for C ruminantium infection. An enlarged spleen is not consistently found in infected animals; Ilemobade and Blotkamp (1978) for example did not find such spleen enlargement in experimentally infected goats. Bezuidenhout and others (1994) acknowledged both lymph node and spleen enlargement, although to a lesser degree than in the present case, in goats and sheep. It is worth commenting that the goat reported here had become infected naturally in the field where other tickborne diseases may have been present. The clinical and pathological findings in the present case, however, are typical of infection with C ruminantium as reported by Smith and Sherman (1994). To the authors' knowledge this report of a natural infection with C ruminantium is the first in Uganda in many decades to have been thoroughly clinically examined. Clinical and pathological diagnosis was confirmed by a brain smear. Many cases of cowdriosis have been reported in the annual reports of the Veterinary Department, Ministry of Agriculture, Animal Industry and Fisheries but remain unconfirmed due to lack of formal diagnosis. This under-reporting does not represent the true extent of the disease in this country. A variegatum can be found on goats, cattle and sheep throughout the country (Okello-Onen 1992) and therefore heartwater is a disease of economic importance to Uganda. With the liberalisation of the economy, exotic breeds of both goats and cattle are being imported to improve the genetic pool of the indigenous animals. Goats such as the Boer for meat and Toggenberg, Saanen and Anglo-Nubian for milk have been introduced. These imported animals are very susceptible to heartwater (Gruss 1983). The goat in the present case was a Toggenberg-Mubende cross. The occurrence of heartwater in this animal emphasises the importance of tick control in the rural areas of Uganda. There is a need to do more extensive epidemiological studies of the disease countrywide and to develop diagnostic tools for use in the field to aid in diagnosis.