Parasitism of Egeria radiata (Lamarck, 1804) in Lower Sanaga Delta, Cameroon: Prevalence, Diversity, Intensity and its impact on this Edible Clam Species

Author(s): Dikoume Mbongo Adolphe, Ajonina Nwutih Gordon, Kojom Foko Loick Pradel, Tomedi Eyango Minette.

Background: Clams are an important source of economic incomes and animal protein source in Cameroon. In contrast, parasitism is a serious threat to the economy and health risk to Cameroonian populations. The present study aimed at determine diversity and intensity of parasitism along with its impact on E. radiata, a major clam species in the country.

Methods: Parasitic screening of freshwater Egeria radiata was carried out December 2017 to July 2018 at lower Sanaga delta in the Littoral region of Cameroon. Bolounga and Maldjedou were local stations of sampling, where clams were collected and in situ measurements of weight, length and width and were transported to the laboratory for parasites survey. Parasites were examined and attempt was made on the identification using appropriate keys.

Results: Statistical analysis of results showed that the parasitic prevalence was 74.5% overall and was 56% and 90% at Bolounga and Maldjedou respectively. The prevalence of parasites habour found were Protozoans (10% vs 0%; p=0.01), Trematodes (4% vs 16.7%; p=0.04), Cestodes (6% vs 23%; p=0.01) and Nematodes (12% vs 31.7%; p=0.01) at respectively Bolounga and Maldjedou stations. Parasites diversity of Egeria radiata show Intensity index at Bolounga and Maldjedou was respectively 1.35 and 1.31 with 1.32 overall. Abundance rate was 0.99 overall and was 0.76 and 1.18 at Bolounga and Maldjedou respectively. Significative correlation can be observed with Burrow and parasitic index ; The size of clams in two stations show lengths (5.2mm vs 4.5mm), height (4.1cm vs 3.5cm), total shell weight (38.9g vs 30.0g) and left shell weight (19.6g vs 15.2g). Higher values were encountered in Maldjedou with significant differences that were observed.

Conclusion: Velocity of parasites inside bivalve species to burrow and filter water expose it to infection with these above mentioned groups of parasites that cause a mass mortality and significant economic losses and public health.