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.

Presenting features of Rhodesian sleeping sickness patients in the Lambwe Valley, Kenya.

During a recent outbreak of Rhodesian sleeping sickness in the Lambwe Valley no asymptomatic Rhodesian sleeping sickness patients were found although 54% of the primary patients had mild symptoms and 9% were stuporous or comatose at presentation. The duration of symptoms was three months or less in 90% of the patients. Headache, weakness, joint and back pains and weight loss were claimed by at least 75% of the patients, while 82% of the females reported amenorrhoea and 70% of the males claimed impotency. Physical examination revealed lymphadenopathy in 86% but fever in only 36% of the patients, while chancres were found in only 16%. Patients had significantly lower levels of haemoglobin and thrombocytes than controls and their erythrocyte sedimentation rates were elevated. A comparison of both blood group and haemoglobin type between patients and controls yielded no significant differences. Fifty-seven per cent of the primary patients reporting mild symptoms had abnormal levels of leucocytes in their CSF. All relapse patients had abnormal CSF parameters. Levels of serum urea nitrogen were significantly elevated in patients, but SGOT, SGPT and total bilirubin were not. Levels of albumin and beta-globulin in patients were significantly lower than controls while gamma-globulin was elevated. Mean serum IgM levels in patients were elevated to nearly three-fold those of controls, but 35% of the individual patient values fell within the 95% range of control values. Some patients had extended prothrombin and thrombin times while fibrinogen levels were significantly elevated. No patients reported haemorrhage, and none was seen.

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.

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.