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PubMed1979

[The epidemiological significance of neo-natal parasitism with microfilariae of Onchocerca volvulus (author's transl)].

Between April 1977 and June 1978, 214 babies born of 210 mothers infected with Onchocerciasis, were examined at the maternity of Po Hospital (Upper Volta). In four of them (1.9%) dermal microfilariae of Onchocerca volvulus were found during the first week after birth. In two other cases microfilariae were seen in the tissue of the umbilical cord. All specimens from placentas and amniotic fluid gave negative results. The infected babies were reexamined monthly monthly from 2 to 18 months, depending on the cases. One child remained positive until the 6th month follow-up. The base-line examination of 5.757 children less than 2 years old from different villages in the WHO Onchocerciasis Control Programme in the Volta River Basin Area showed that 1% of children less than one year old and 2% of children of 12 to 23 months old were carriers of dermal microfilariae. These results indicate that in meso- or hyperendemic areas children less than one year old and carriers of microfilariae of Onchocerca volbulus may have been infected in utero. The existence of such cases, in an area of vector control, does not prove a residual vector borne transmission.

Burkina Faso↗

PubMed1979

The development of Onchocerca volvulus in two temperate blackfly species, Simulium ornatum Meigen and Simulium lineatum Meigen.

In view of the promise shown by temperate simuliids for laboratory colonization, the ability of Simulium ornatum and S. lineatum to support the development of Onchocerca volvulus was investigated. An injection technique is described for the introduction of O. volvulus microfilariae from a chimpanzee into female simuliids in the absence of a bloodmeal. RPMI 1640 medium, with penicillin, streptomycin and foetal calf serum, proved satisfactory as an inoculation medium. Third stage larvae were obtained in both S. ornatum and S. lineatum after seven days at 27 degrees C. The rate of development of the parasite in S. ornatum is recorded.

Animals↗

PubMed1976

Antigenic diversity among Onchocerca volvulus in Nigeria, and immunological differences between onchocerciasis in the savanna and forest of Cameroon.

Onchocerciasis is a remarkably chronic infection and, in West Africa, there are distinct clinical and pathological differences between the disease in the savanna and in the forest. Experiments were carried out to see whether antigenic diversity among Ochocerca volvulus worms might contribute to these features. Extracts of adult worms and or microfilariae were analysed by disc electrophoresis on polyacrylamide gels and showed a remarkable diversity of protein patterns but no consistent savanna/forest or Nigeria/Cameroon differences. Indirect haemagglutination using cross-absorbed sera was used to look for antigenic diversity or identity between different O. volvulus worms. Sera of patients were absorbed with antigens extracted from worms taken from those paitents and then titrated against sheep erythrocytes coated with the same antigens. It was shown that an adult Onchocerca volvulus could be either antigenically identical with, or distinct from, another worm taken from the same patient. In one Nigerian village identity was shown in two instances nad diversity in five. Microfilariae lack some antigens possessed by adult worms. This test has shown consistent savanna/forest differences in worm antigen patterns and antibody responses. In order to explain the pattern of these differences it was necessary to postulate that forest patients possessed antibodies to another worm which had antigens in common with savanna Onchocerca. The relevance of these findings to the pathology and prevention of onchocerciasis is discussed.

Antigens↗

PubMed1977

Preliminary studies on the histochemical differentiation of strains of Onchocerca volvulus microfilariae in Togo.

Skin snips were taken from 75 people living in four villages of northern Togo. The 7824 microfilariae that emerged were examined by staining for the presence of acid phosphatase. Four distinct patterns of enzyme staining were observed, and descriptions of the stained microfilariae are given. The study confirms the view that a number of biological strains or variants of Onchocerca volvulus coexist in West Africa, and suggestions are made for further research that could result in the practical application of these observations in onchocerciasis control programmes.

Animals↗

PubMed1977