Wesselsbron disease virus associated with abortions in goats in Botswana.

Abstract

Brucella melitensis Chlamydia psittaci Toxoplasma gondii Rift Valley Fever virus Bluetongue viruses Wesselsbron disease virus ,8 ,8 ,8 ,8 ,8 ,8 ,8 ,8 ,8 ,8 ,8 $80 Wesselsbron disease (WSL) is an acute mosquitoe-borne flavivirus infection of sheep, cattle, and goats; it is characterized by high mortality in newborn lambs and kids.6 In adult animals, there may be an inapparent disease with occasional abortions. The disease was first described in 1955 when neonatal deaths and abortions occurred in a flock of sheep in the Wesselsbron district of the Orange Free State in South Africa.7 Experimental WSL virus infection also can cause embryonic fetal death and unnoticed loss of the conceptus or overt abortion.6 In this report, we describe the serologic diagnosis of WSL as the probable cause of abortion in 4 goat does on a farm in Gaborone, Botswana. In July 1995, a farmer reported that 4 goats had aborted. The farm had 50 goats that were Tswana or Tswana–Boer crosses. There were also 35 indigenous sheep, but no abortions were reported from the sheep. Sera were collected at abortion and 3 weeks later and tested for antibodies to various potential abortifacient agents. At the Onderstepoort Veterinary Institute (Pretoria, South Africa), the enzyme-linked immunosorbent assay3 was used to identify antibodies to bluetongue and Rift Valley fever viruses, and the hemagglutination inhibition test was used to identify antibodies to WSL virus. Commercial kitsa and internationally accepted methods5,8 were used to identify antibodies to Chlamydia psittaci var. ovis, Toxoplasma gondii, and Brucella melitensis. All 4 goats that aborted were about 1.5 years old. The abortions occurred during the early stages of gestation, but the aborted fetuses could not be found. On clinical examination, the mucous membranes were slightly pale. Ocular and vaginal swabs were negative for Chlamydia and other pathogenic bacteria. Microscopic examination of Giemsa-stained blood smears did not reveal any hemoparasites. The fecal worm egg count after floatation in saturated sodium chloride solution showed a mean of 1,000 strongyle eggs/g. Serologic studies of all 4 goats showed seroconversion to WSL virus but not to other agents for which antibodies were tested (Table 1). The causes of infertility and abortions in goats may include poisons, injuries, nutritional deficiencies, and infectious diseases.2,4 Infectious agents are often difficult to isolate because some pathogens, particularly viruses, may no longer be present or detectable when abortion occurs. Serologic tests for the presence of antibodies may be a more reliable method for identifying these agents. In the present