Endemic stability for Theileria parva infections in Ankole calves of the Ankole ranching scheme, Uganda.

A population-based study was carried out on the Ankole ranching scheme in south-west Uganda with the aim of determining the endemic status of Theileria parva infections. For this purpose, the age-related sero-prevalence of T. parva and the specific calf mortality associated with the parasite were assessed. Blood samples were collected from 931 Ankole calves of up to 12 months of age from 81 randomly selected herds. The relationship between rainfall pattern and whole-body Rhipicephalus appendiculatus counts was determined. The influence of tick control practices on East Coast fever-related calf mortality, and sero-positivity were also determined. A significant (r2 = 0.76, P = 0.000) association between R. appendiculatus counts and rainfall was observed. There was no significant (P > 0.05) association between theileriosis-related calf mortality, sero-positivity and the different tick control practices. Antibody prevalence based on the PIM ELISA was above 70% among calves of 6 months of age in 96% in all the herds. Theileria parva-related calf mortality determined by repeated herd visits and farm records ranged between 0 % and 5.4 %. It was concluded that endemic stability for theileriosis, caused by T. parva, existed in the study area, and that the risk of the occurrence of economically important outbreaks of East Coast fever in indigenous cattle was regarded as minimal under the prevailing conditions.

Absence of perinatal transmission of blood-borne non-A, non-B hepatitis virus by chimpanzees with acute and chronic infection.

Two chimpanzees were born to parents with chronic non-A, non-B hepatitis and remained with their mothers until 12 and 18 months, respectively. The infants were followed from 7 to 8 weeks of age with biweekly or monthly blood samples and with monthly liver biopsies from 4 to 7 months after birth. Another chimpanzee, along with both of its parents, was held throughout the parents' acute infection with non-A, non-B hepatitis; at this time the infant was 14-16 months of age, and it was followed with bi-weekly blood samples and monthly biopsies from the time of potential exposure for 20 months. No abnormalities indicative of non-A, non-B hepatitis were detected in these animals. During the 29 to 35 months of follow-up, alanine aminotransferases and gamma glutamyl-transferases (GGPT) levels remained well within normal range for animals held in the same facility. Histologic and electron microscopic examination of liver tissue revealed no abnormalities.

Failure of a human immunodeficiency virus (HIV) immune globulin to protect chimpanzees against experimental challenge with HIV.

To assess the possible efficacy of passive immunization against human immunodeficiency virus (HIV) an immune globulin was prepared from plasma of HIV-seropositive donors selected to be among those having the top 12.5% of virus-neutralizing antibody titers. The immune globulin was treated with pepsin to render it intravenously tolerable. The preparation, which we termed HIVIG, neutralized 100 tissue culture 50% infective doses (TCID50) of HIV at an average dilution of 1:1000 in neutralization tests in vitro. During preparation HIVIG was subjected to virus inactivation and removal procedures that in theory resulted in a reduction in HIV infectivity by a factor of 10(25). At a dose of 9-10 ml/kg of body weight both the virus-inactivated source plasma and the final immunoglobulin preparation were noninfective and without adverse effect in two chimpanzees. Two chimpanzees inoculated intravenously with HIVIG at 1 ml/kg and two inoculated with 10 ml/kg were challenged intravenously 1 day later with 400 TCID50 of the same strain of HIV (HTLV-IIIb) used in neutralization assays in vitro. All animals became infected. Incubation periods to virus isolation (by cocultivation with human mononuclear cells) in HIVIG recipients did not differ significantly from the incubation period seen in a control animal that received a normal anti-HIV-free immunoglobulin. These findings may have implications for understanding the failure of experimental vaccines to protect against HIV challenge in chimpanzee experiments.