Diagnosis of Rhodesian sleeping sickness in the Lambwe Valley (1980-1984).

In primary Rhodesian sleeping sickness patients, parasitological diagnosis was best performed by rodent inoculation of blood (98.5%+) followed by Giemsa-stained thick blood smears (93.3%+). Parasitological diagnosis in relapse patients was sometimes impossible and clinical diagnosis based on CSF examination was necessary. Early during a disease outbreak in 1980, 89% of the infections were detected by mobile field teams, but once established in the endemic area a stationary diagnostic facility detected most of the cases. A total number of 23,751 examinations for Rhodesian sleeping sickness and malaria were made by mobile field teams during 1980-1984; 102 primary cases (0.43%) and 25 (0.10%) relapse cases were diagnosed. A total of 9339 individuals (39%) had patent malaria infections. The IFAT was positive in 89% of the primary sleeping sickness patients and 77% of the relapse patients. Seventy-nine per cent of the primary patients were positive in a CFT test, and 77% of the relapse patients were considered positive.

Demographic characteristics of the Lambwe Valley population.

Thirty-four per cent of the population (11,079) in the Lambwe Valley study site was under the age of 10, and 59% were under the age of 20. The population was equally divided among males and females (M/F 0.99). The crude birth rate averaged 45%; the death rate was 8% and the natural increase averaged 37%. Infant and child mortality was 66% and 108% respectively. The average household size was 8.4 individuals. The population migrated to the Lambwe Valley primarily from other areas in Kenya, although 13% were from Tanzania. The predominant tribal group was Luo (59%) followed by the Abasuba (38%). A few Luyha and Kisii were also encountered. Population increased by 3.5-fold in the 1960s, followed by a 2.5-fold increase in the 1970s. Due to an aerial spray tsetse control programme, sleeping sickness had a low prevalence in October 1981 (one of 5749). Of 339 individuals confirmed as sleeping sickness patients by hospital records from within the study site 320 (94.3%) were traced to their homes. Mortality in domestic cattle (40%), goats (47%), sheep (55%), and dogs (50%) had occurred over the previous two years during an outbreak of trypanosomiasis.

PIP: 34% of the population (11,079) in the Lambwe Valley study site are under the age of 10 and 59% are under age 20. The population is equally divided among males and females (M/F 0.99). The crude birth averaged 45%, the death rate 8%, and the natural increase 37%. Infant and child mortality was 66% and 108% respectively. The average household size was 8.4 individuals. The population migrated to the Lambwe Valley primarily from other areas in Kenya, although 13% were from Tanzania. The predominant tribal group was Luo (59%), followed by the Abasuba (38%). A few Luyha and Kisii were also encountered. The population increased by 3.5-fold in the 1960s followed by a 2.5-fold increase in the 1970s. Due to an aerial spray tsetse control program, sleeping sickness had a low prevalence in October 1981 (1 of 5749). Of 339 individuals confirmed as sleeping sickness patients by hospital records from within the study site. 320 (94.3%) were traced to their homes. Mortality among domestic cattle (40%), goats (47%), sheep (55%), and dogs (50%) had occurred over the previous 2 years during an outbreak of trypanosomiasis.

Epidemiology of Rhodesian sleeping sickness in the Lambwe Valley, Kenya.

A total of 912 cases of sleeping sickness have been recorded from the Lambwe Valley from 1959 to 1984. After a period of decreasing prevalence in the 1970s an outbreak of disease occurred between 1980 and 1984. The incidence of disease for this five-year period was highest in areas adjoining the Ruma National Park, reaching 54% in Area I. Attack rates were highest in the 50+ age group (125) and children had significantly lower attack rates (8%) in this area of peridomestic transmission. Sex ratios of patients (M/F) were near 1.0 in areas in closest proximity to the thickets in the National Park, while in distant areas the ratios rose to 6.0. The distribution of the number of patients within different households was studied; fewer households than expected had 0 or one patient, and more than expected had three or more patients. No difference in attack rates were found between Nilotic and Bantu groups. Twelve different zymodemes were found in 136 stocks of Trypanosoma brucei rhodesiense. Four new zymodemes appeared in 1980 in the latest outbreak and accounted for 73% of the stocks isolated from man during this outbreak. Neutralization tests indicated that each trypanosome zymodeme may also represent a different serodeme.

Treatment of Rhodesian sleeping sickness in Kenya.

In a study of 269 sleeping sickness patients treated with Mel-B, 14 (5.2%) died during treatment. With total dosages of at least 30 ml (1.08 g), 1.4% relapsed and another 6.4% died, mostly of unknown causes, within three years of treatment, giving a success rate of 92.1% over the three years. Mel-B was used to treat 55 relapses after suramin therapy with 1.8% deaths during treatment, 3.6% relapses, and 92.7% success over at least three years. Apparent drug resistance to Mel-B was found in three patients who continued to relapse after repeated treatments. During 1980, 51 patients were treated with suramin on the basis of clinical condition without benefit of cerebrospinal fluid (CSF) analysis. Subsequently 49% of these patients relapsed within three years of treatment. When 29 patients were treated on the basis of CSF evaluation only two (7%) relapsed.

Regional variation in prevalence of antibody against human T-lymphotropic virus types I and III in Kenya, East Africa.

The prevalence of antibodies against HTLV-III and -I was studied among populations of 6 distinctly different regions of Kenya, an equatorial African country in which AIDS has rarely been observed. Overall, 21% of subjects had ELISA reactions suggesting the presence of antibody against HTLV-III. The frequency of HTLV-III antibodies was highest among the Turkana people (50%) and lowest among the Masai (8%). Prevalence increased with age but was not related to sex. The pattern of ELISA-detected antibody against HTLV-I was similar. The specificity of these antibodies was supported by Western blot analysis of a subset of sera with high and low ELISA ratios, in which 66% and 73% of those with ELISA ratios considered positive (= greater than 5.0 in this study) also had a profile of bands consistent with HTLV-III and HTLV-I respectively. The antibodies detected were not cross-reactive between HTLV-III and HTLV-I on Western blot analysis. In a series of subjects with various parasitic and infectious diseases, patients with idiopathic splenomegaly and with schistosomiasis had a high proportion of antibodies against both HTLV-III and HTLV-I. This survey shows that reactivity in the ELISA HTLV-III and HTLV-I assays are common among Kenyans but vary considerably by region.

Effect of targeted mass treatment on intensity of infection and morbidity in schistosomiasis mansoni. 3-year follow-up of a community in Machakos, Kenya.

The effect of targeted mass treatment, a new strategy for cost-effective control of schistosomiasis mansoni based on administering single-dose chemotherapeutic agents to individuals with disease manifestations (hepatosplenomegaly) or heavy infections, was evaluated in an endemic area in Kenya. Two years after treatment of subjects with hepatosplenomegaly, the mean liver midsternal-line measurement decreased from 6 x 5 +/- 0 x 6 to 2 x 9 +/- 0 x 5 cm and the mean faecal egg count dropped significantly from its pretreatment level of 1090 +/- 290/g to 88 +/- 31/g. Targeted chemotherapy was then administered to a group of 122 subjects with faecal egg counts greater than or equal to 400/g. A similar maintained decrease in egg counts after chemotherapy was demonstrated in this group; mean egg count after one year was 115 +/- 17/g compared with 1250 +/- 232/g before treatment. The yearly rate of acquisition of heavy infection in this community was low (7%) and did not differ significantly in the uninfected, lightly infected, or heavily infected (and treated) groups.

Functional studies on purified eosinophils and neutrophils from patients with Schistosoma mansoni infections.

Unpurified peripheral blood leucocytes or purified eosinophils and neutrophils from patients with schistosomiasis and from normal individuals were compared for their ability to interact with antibody coated schistosomula of Schistosoma mansoni. There was no difference in the ability of buffy coat cells or neutrophils from patients and from normal individuals to mediate antibody-dependent 51Cr release from labelled schistosomula. However, eosinophils from patients were significantly better than those from normal individuals in causing antibody-dependent 51Cr release. This enhanced activity of eosinophils from patients with schistosomiasis was found to correlate with the intensity of their infection as judged by faecal egg counts. Eosinophils from patients also contained a higher proportion of cells with detectable Fc receptors than those from normal individuals. It is suggested that the difference in the behaviour of eosinophils from patients and from normals may reflect an 'activated' state of these cells in the infected individuals.

A new method for the purification of human eosinophils and neutrophils, and a comparison of the ability of these cells to damage schistosomula of Schistosoma mansoni.

Centrifugation of human white blood cells over either Ficoll-Hypaque or slightly hypertonic Metrizamide discontinuous gradients reliably produces separate fractions that are enriched for either neutrophilic or eosinophilic granulocytes. This single step purification routinely yields 90 to 100% pure neutrophils and 85 to 100% pure eosinophils. Metrizamide gradients, in particular, reproducibly provide high yields of 90 to 100% pure eosinophils from normal subjects with 2 to 3% eosinophils in their peripheral blood. The method does not damage cells as judged by morphologic or functional criteria. The purified cell populations were tested for their ability to damage antibody-coated schistosomula either by the measurement of 51Cr release from labeled organisms, or by direct morphologic assessment. Neutrophils were superior in their ability to release 51Cr from labeled organisms, but eosinophils adhered to the organisms to a greater extent and induced microscopically detectable damage.