Feasibility of Onchocerciasis Elimination with Ivermectin Treatment in Endemic Foci in Africa: First Evidence from Studies in Mali and Senegal

The control of onchocerciasis, or river blindness, is based on annual or six-monthly ivermectin treatment of populations at risk. This has been effective in controlling the disease as a public health problem, but it is not known whether it can also eliminate infection and transmission to the extent that treatment can be safely stopped. Many doubt that this is feasible in Africa. A study was undertaken in three hyperendemic onchocerciasis foci in Mali and Senegal where treatment has been given for 15 to 17 years. The results showed that only few infections remained in the human population and that transmission levels were everywhere below postulated thresholds for elimination. Treatment was subsequently stopped in test areas in each focus, and follow-up evaluations did not detect any recrudescence of infection or transmission. Hence, the study has provided the first evidence that onchocerciasis elimination is feasible with ivermectin treatment in some endemic foci in Africa. Although further studies are needed to determine to what extent these findings can be extrapolated to other areas in Africa, the principle of onchocerciasis elimination with ivermectin treatment has been established

Appraisal of the status of bovine trypanosomiasis around the summit areas of the Jos Plateau, Nigeria

A parasitological survey of blood samples of 200 calves, yearlings and adults of zebu cattle for infecting  Trypanosoma species, the causative agents of bovine trypanosomiasis in Jos, Babale and Federe areas revealed an overall percentage infection of 7.5%. Thin film technique and haematocrit centrifugation diagnostic methods were used. Three Trypanosoma species namely T. Brucei, T. Vivax,, and T. Congolense were identified. Di.fferences in infection were not indicated between yearlings and calves (X2 = 0.389, P>O. 05), but between adults and claves, the pattern of infection was significant (X2 = 6.394, P>0.05) for the sam-ples taken from Babale. Males from Nara'guta and Federe were significantly (P<0.05) more parasititized than the males, while at Jos,females were the sole carriers of the infections. Our findings show a recrudescence of bovine trypanosomiasis and a gradual build up of the infection over a ten-year period since the last outbreak and control of the disease on the Plateau. More studies to cover a wider of the Plateau are now required to determine the spread and pattern of the disease, as well as the apparent variation in the prevalence rates observed between the sexes. A study of the species composition of the vectors and population dynamics in relation to the transmission ofbavine trypanosomiasis on the Plateau is also advocated

Baboons as potential reservoirs of zoonotic gastrointestinal parasite infections at Yankari National Park, Nigeria

Background: Zoonoses pose a risk to public health.Objective: To carry out the investigation of the prevalence of  gastrointestinal parasites of baboons, Papio anubis, frequenting the Wikki base Camp in Yankari National Park, NigeriaMethod: Formol-ether concentration technique was used to isolate parasite eggs and cysts from faecal samples.Results: Parasites recovered were Ascaris lumbricoides, Ancylostoma duodenale, Strongyloides stercoralis, Fasciola sp, Schistosoma mansoni, Hymenolepis nana, and Trichostrongylus sp, and cysts of protozoan  parasites Entomoeba histolytica, E. coli, and Iodamoeba butschii.Conclusion: Most of the parasites identified are known to have high pathologic involvement in humans, implicating the baboons as potential source and reservoirs for human zoonotic parasitic infections although further molecular work would be necessary to ascertain if these  gastrointestinal parasites are the same strains that infect humansKeywords: Papio anubis, gastrointestinal parasites, zoonoses, Yankar

Acid phosphatase staining variations in Onchocerca volvulus microfilariae from Guinea Savanna of Nasarawa State, Nigeria

Despite resounding control achievements in some areas of West Africa and the Americas, a recent estimate indicated that at least 37 million people remain infected mostly in Africa. The epidemiology of human onchocerciasis in various endemic areas of Africa and Latin America has been attributed to the existence of geographical strains of filarial parasitic Onchocerca (O.) volvulus. Studies were conducted in two endemic villages in Nasarawa State by staining of microfilariae for acid phosphatase activity after skin snipping with corneo-scleral punch. The result showed that forty eight (48%) percent of those sampled carried microfilariae. Two thousand, two hundred and fourteen (2, 214) microfilariae were stained. Four hundred and twenty nine (429) 19.4% followed the staining patterns described by previous workers as patterns V, VIII and XII. One thousand, seven hundred and eighty five (1,785=80.6%) had a different and new staining pattern. This suggested that O. volvolus in Akwanga Area of Nasarawa State is a different strain from those identified in Sudan savanna, Rainforest and the mountains of Jos Plateau. It was recommended that proper identification of species strains combined with proper study on vector and transmission patterns may lead to an integrated control strategy instead of relying on any one control method.Keywords: acid phosphatase, staining variation, microfilariae, Onchocerca volvulus, Nasarawa StateNigerian Journal of Parasitology, Vol. 32 [2] September 2011, pp.157-16

Sex chromosome variation and cytotaxonomy of the onchocerciasis vector Simulium squamosum in Cameroon and Nigeria.

On the basis of sex chromosome variation, three cytotypes of Simulium squamosum (Enderlein) (Diptera: Simuliidae) are described from Cameroon and Nigeria. Simulium squamosum A is the typical form as originally described by Vajime & Dunbar (1975) with chromosome I as the sex chromosome. It occurs throughout most of Cameroon and south-east Nigeria. A second cytotype, S. squamosum B, is described from the river Sanaga (Cameroon). It also has chromosome I as the sex chromosome, but the nature of the sex differential region is different. Simulium squamosum C has no sex-linked chromosomal rearrangements. It is widespread in Nigeria and occurs near Mount Cameroon, where it seems to hybridize with S. squamosum A

A guide to the Simulium damnosum complex (Diptera: Simuliidae) in Nigeria, with a cytotaxonomic key for the identification of the sibling species.

<title/> Although approximately 40% of all the people blinded by Onchocerca volvulus are Nigerians, almost nothing was known about the various cytospecies of the blackfly vectors present in Nigeria until 1981. The activation of the Nigerian National Onchocerciasis Control Programme in 1986 (and that programme's initiation of mass distributions of ivermectin in 1991) provided a significant stimulus to understand the biology of the Nigerian vectors but the exploration of any possible differences between the cytospecies has been hampered by a lack of accessible taxonomic information. This review attempts to satisfy that need. There are nine different cytoforms reliably recorded from Nigeria (Simulium damnosum s.s. Nile form, S. damnosum s.s. Volta form, S. sirbanum Sirba form, S. sirbanum Sudanense form, S. soubrense Beffa form, S. squamosum A, S. squamosum B, S. squamosum C and S. yahense typical form), and three more are known from surrounding countries and might be reasonably expected to occur in Nigeria. All of these cytospecies are presumed to be vectors, although there have been almost no identifications of the vectors of O. volvulus in Nigeria. The biogeographical distribution of the cytoforms is broadly similar to that known in other parts of West Africa (although many of the cytoforms remain insufficiently studied). The physico-chemical hydrology of the Nigerian breeding sites of the cytospecies does not, however, correspond to that seen elsewhere in West Africa, and it is not clear whether this might be related to differences in the cytoforms. An illustrated cytotaxonomic key is presented to facilitate and encourage future studies