Characterization Of Cattle Filarial Parasite Morphologically Similar To Wuchereria Bancroft (Nematoda Filaroidae) In Southern Ghana

Abstract

The monitoring of the current global strategy for the elimination of lymphatic filariasis (LF) can be confounded if other parasites indistinguishable from Wuchereria bancrofti also occur in endemic areas. An incidental examination of cattle blood revealed microfilariae that were morphologically similar to W. bancrofti. This study was therefore conducted to characterize these cattle filarial parasite. A total of 284 cattle from Somanya, Winneba and Axim were screened randomly for filarial parasites using the traditional blood smear technique. Blood was collected from the positive cattle at 4-hour intervals over a 24-hour period to determine microfilarial intensity and periodicity, and for molecular studies.Six hundred and ninety mosquitoes were collected off the positive cattle from 00.00 - 04.00am by an aspirator into paper cups and sent to the laboratory. The mosquitoes were morphologically identified and dissected for filarial infections. DNA extracted from the microfilariae (mf) and infective stages (L3s) of the parasites were subjected to PCR analysis using W. bancrofti primers (NV1 and NV2). The prevalence of filarial infections were 3.5% (5/141) and 6% (2/33) at Winneba and Somanya respectively and negative for 110 cattle blood screened at Axim. An overall prevalence of filarial infections among cattle for the three study sites was found to be 2.4% (7/286). The geometric mean densities among infected cattle were found to vary between 4.6-20 microfilariae/1 OOul of blood and trend suggestive of subperiodicity. The two morphological types of microfilariae (sheathed and unsheathed) were observed and both were morphometrically similar, but different from W. bancrofti suggesting that they were not the latter species but rather Setaria species. One distinctive feature about the microfilaria was the presence of a prominent inner korper, which is absent in W. bancrofti. Also both cattle filarial parasites and the infective larvae were negative by PCR. Thus indicating that they are not W. bancrofti. Among the 690 mosquitoes collected off cattie, 612 (88.7%) were Culex, 29 (4.93%), Anopheles, 43 (6.23%) Mansonia and 1 (0.15%) Aedes. Two infective stages of filarial worms (L3) were found in Culex mosquitoes. These results seem to indicate that the presence of these cattle filarial parasite in LF endemic areas may not confound the monitoring of LF intervention programmes.