Determination of Microsporidia Infection in Larvae and Adult Anopheles Mosquitoes (Diptera: Culicidae) Northwest Ethiopia



Background: Microsporidia are a diverse group of obligate intracellular, spore forming parasites that infect all phyla of invertebrates. Microsporidia are known to infect a wide variety of animals including mosquitoes. A few studies showed that microsporidia infection of mosquitoes is associated with larval mortality or reduced adult fecundity and lifespan. The aim of this study is to determine microsporidia infection in field collected Anopheles larvae and reared adults.

Methods: Anopheles larvae were collected from the field and analyzed from February to April 2022. The 4th stage larvae, after determining the species identity, they were dissected to extract their midgut while the early stage larvae were transported to entomological laboratory for reareing the adult in the insectary room. Similarly, after determining the species identity they were dissected to extract their midgut. Then two thin smears for each dissected larvae and/ adult were made. Fixed preparations were stained with Giemsa and modified Ziehl-Neelsen staining techniques to detect the microsporidia. Descriptive statistics and independent t-test were used to analyze the data.

Results: Anopheles gambiae complex was identified as the most predominant species from field collected larvae and insectary reared adults. From the total 258 larvae and 258 adult An.gambiae complexes tissue smears examined, microsporidia were detected in 2.7% [7/258, (95%, CI: 0.8-5)] and 1.2% [3/258, (95%, CI: 0.01-2.7)] of larvae and adult respectively. The mean density of microsporidia in larvae and adults were 64.9 (± 23.4 SD) and 36 (± 8.5SD) respectively. The difference of microsporidia density between infected larvae and adults was statistically significant (F=1.77, P= 0.02).  

Conclusion: Significant level of microsporidia infection was detected using light microscopy. Further microsporidia identification down to the genus and species level needs to determine its ultrastructure characteristics and the comparative analysis of small subunit rRNA sequence data.

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