Abstract:
Prevalence of human onchocerciasis in Tanzania is
described. The prevalence is high in Bwakira (63.6%), Mahenge
(58.6%) and Ruvuma (31.9%); and low in Amani (22.4%) when
compared to that reported in 1970. The increase and decrease
on the prevalence indicate that the disease transmission has
been increasing or decreasing in the respective foci. It is
speculated that bush-clearing and deforestation in general,
had positive effects on the transmission of the disease where
Simulium damnosum complex is a vector and the negative
effects with Simulium neavei complex.
In this study, Indirect Haemagglutination Antibody (IHA)
test was also established for serodiagnosis of
onchocerciasis, using crude heterologous antigen of adult
Onchocerca gutturosa. with this antigen, IHA titres (serum
•dilutions) of 1/320 and above were used as positive for
onchocerciasis because they discriminated 8ross-reaction
effects due to other helminths and under these circumstances,
the IRA test was considered to be sufficiently valid for the
diagnosis of the disease in Tanzania.
The established IHA test for diagnosing onchocerciasis was
found to be complementary to the skin snip and clinical
diagnostic methods. High sensitivity of the IHA test was
found in Amani (93.7%), Bwak i r a (89.7%), Kilosa (81.8%) and
(iv)
and Ruvuma (75.0%) foci. However, the IHA test was complementary
to the parasitological diagnosis in assessing age disribution of
the disease.
There was significant association between IHA
response and parasitological diagnosis, and skin changes due to
onchocerciasis in certain foci; indicating a well established
balance between the Q.volvulus parasite and the host, and also
emphasizing the importance of IHA test in ascertaining the disease
in these people with skin changes due to disease.
A report on the development of Q,gutturosa to infective stage
in Simulium vorax Pomeroy is presented (Appendix D4).
A more
descriptive report on Q,gutturosa in Tanzania cattle is presented!
(Appendix D3). This second report highlights the importance of
continuing checking for Q,gutturosa in cattle in all areas where
the presence of Q,volvulus has been'established, because there is
evidence that S,vorax which transmits Q,gutturosa in cattle is also
a potential vector of Q,volyulus, Raising infective stage larvae
of Q. gutturosa in S .yorax for antigen was attempted.
But the
average number (2.3) 6f the microfilariae per fly, taken during the
infective blood~mealfrom a cow infected with the parasite, was
considered to be quite small for sufficient recovery to provide
sufficient amount of the infective stage larvae for antigen.
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