Serologic markers for hepatitis B virus and hepatitis A virus in Bushmen in West Caprivi, Namibia.

A community based sero-epidemiological study was undertaken to determine the age specific prevalence rates of hepatitis A virus (HAV) and hepatitis B virus (HBV) infection in a band of Bushmen in the West Caprivi, Namibia. All children tested and all but two of the adults tested showed the presence of anti-HAV antibodies. Nineteen individuals (18%) were positive for HBsAg and 65 (61%) individuals had serologic evidence of past exposure to HBV infection.

African trypanosomiasis: haematogenic brain parasitism early in experimental infection through bypassing the blood-brain barrier, with considerations on brain trypanosomiasis in man.

A hematogenic invasion of the brain in suckling NMRI mice infected with Trypanosoma brucei rhodesiense was initiated by means of a mechanical damage of the blood-brain barrier. The brain was punctured after development of a blood infection. Brain infection was found in 31 out of 32 animals examined. Trypanosomes are initially capable of rapid multiplication. The number of parasites was highest during the 1st week. From the middle of the 2nd week the number of parasites decreased continuously, alongside increasing atrophy. In the 3rd and 4th week only rare degenerating or ghost trypanosomes were present. No reactions were detected in the glial and mesenchymal cells. It is presumed that the short phase of trypanosome multiplication is due to the temporary collateral oedema of the brain tissue. The decrease in parasites from the 2nd week onwards is mainly attributed to natural death due to particular anatomical features of the brain tissue. These are also responsible for the absence of defensive inflammatory reactions, based on the hypothesis that contact between trypanosomes and the cells of the brain blood vessels is prevented.

Development of Trypanosoma brucei in suckling mouse brain following intracerebral injection.

Intracerebral inoculation of Trypanosoma b. brucei and T. b. rhodesiense into suckling mice produced infection of brain tissue which subsequently gave rise to an infection of the blood and other tissues, in which a normal histopathological picture was observed. Treatment of other intracerebrally infected sucklings with 5 mg/kg diminazene aceturate (Berenil) to clear the infection from the blood permitted a study of the course of the infection in the brain without interference from pathological processes induced by bloodstream infections. There was rapid multiplication and migration of trypanosomes throughout the brain of mice. Pathological processes normally seen in experimental central nervous system infections were absent, except in a single mouse treated earlier with Berenil which developed meningo-encephalitis with trypanosomes present in the choroid plexus. The possible use of such a model system in chemotherapeutic studies is discussed.

Specificity of the Testryp CATT card agglutination test in a non-sleeping-sickness area of Africa.

A card agglutination test (CATT), recently developed for the diagnosis of trypanosomiasis, has been evaluated in certain southern African localities; 179 blood specimens and 63 serum samples from black patients of both sexes and widely ranging ages, suffering from a variety of generalized and parasitic disorders, were tested. False-positives were minimal (2.9%) and there were no cross-reactions with any of the parasitic infections. The CATT is therefore regarded as a highly specific and sensitive test, which can be performed effectively in the field by non-specialist personnel.

African trypanosomiasis: treatment-induced invasion of brain and encephalitis.

Histological sections of the brain from Microtus montanus infected with Trypanosoma rhodesiense and treated after the initial infection period showed that trypanosomes promptly invade the brain tissue and induce a severe encephalitis within a very short time. These findings suggest that the brain invasion and encephalitis that occur after treatment in sleeping sickness must be considered an effect of the treatment. The results illustrate that the brain invasion is probably not hematogenic but rather due to a process of parasite migration from the subarachnoidal space over the Virchow-Robin spaces into the brain.

Experimental Trypanosoma (Nannomonas) congolense infection in Microtus montanus.

Seventy-two voles (Microtus montanus) were infected with a strain of Trypanosoma congolense of low virulence in mice to study their susceptibility and value as a tool for testing chemotherapeutic agents. The infection in Microtus was highly virulent. Parasitaemia was low to moderate. Significant spleen and body weight changes were observed. Blood capillaries of the heart, brain, kidneys and lungs were markedly dilated and numerous parasites were present in the dilatations, particularly in the heart. There was a generalized serous inflammation, often associated with histiocytic interstitial lesions (except in the brain), particularly in the heart. Treatment of voles with diamidines on cumulative mortality day 60% gave a complete cure.

Experimental chronic Trypanosoma brucei rhodesiense infection in Microtus montanus.

Adult Microtus montanus were inoculated with a recently isolated strain of Trypanosoma brucei rhodesiense of human origin. The animals developed subacute to chronic infection and low-grade parasitemia. Histopathological examination of the heart revealed a severe pancarditis resulting in pronounced weight loss, and survival times of 5-8 weeks, preventing development of meningoencephalitis. In the brain a moderate meningitis was found, usually associated with moderate numbers of parasites in the choroid plexus and leptomeninges; however, trypanosomes were also found without tissue inflammation. Meningoencephalitis was found after 7 weeks, with parasites in the cerebral parenchyma. Chronic inflammation was present in lungs and kidney, often associated with trypanosomes; in one animal glomerulonephritis was found. Spleen and lymph glands showed a variable degree of lymphoid hyperplasia but no extravascular parasites. In the liver of all animals plasmolymphoid infiltrates were observed in the periportal connective tissue; no extravascular parasites were observed. A variable degree of lymphoplasmohistiocytic infiltrate in the connective tissue and occasional rare trypanosomes were seen in mesenterium, pancreas, epididymis, striated muscle, and skin. Experimental infection in M. montanus appears to be a suitable model for study of the acute trypanosomiasis of T. b. rhodesiense, but not for chronic African sleeping sickness with cerebral involvement.