DETECTION OF A PARASITIC MICROSPORIDIA ISOLATED FROM FARMED AND WILD SHRIMP IN NORTHWEST MEXICO

The presence of pathologies in aquatic crops as well as in fisheries is a serious problem for the aquaculture industry. Microsporidiosis is a disease caused by an obligate intracellular parasite corresponding to the Microspora phylum, and has gained great relevance due to the severe damage and economic impact on cultured and wild captured shrimp. The aim of this project is to identify the microsporidium that causes milk shrimp muscle in farmed and wild shrimp in Northwestern Mexico through histological and molecular analysis.

Shrimp samples (8 g average weight) were collected with signs of milk abdominal muscle (Fig. 1) in farms and fishing regions of Southern Sonora, Sinaloa and Nayarit. The analysis performed at the Aquatic Health Laboratory (Laboratorio de Análisis de Sanidad Acuícola) of the Instituto Tecnológico de Sonora, included histopathology (Hematoxylin-Eosin) with fixed whole organisms to determine the cellular damage of the infection in different shrimp tissues; with endpoint PCR and sequencing, the genus of the associated microsporidia was determined.

The incidence of infected shrimp (milk muscle) appeared in farms of the three states, but in captured wild shrimp was detected only in Sonora and Sinaloa. An abundant invasion of spores (2 µm) in abdominal muscle tissue, and a lesser presence in the intestine, hepatopancreas and pleopods was determined by histopathology (Fig. 2). The infected species correspond to Penaeus vannamei and P. stylirostris.

Initially, DNA from infected tissue samples was used to amplify the 18S rDNA gene by PCR. 1,200 bp fragments were obtained and sequenced. The microsporidia identification corresponds to Perezia sp. (previously Pleistophora sp.), according to the Genebank database of NCBI. Another PCR analysis with high quality DNA and specific primers CDS (Cotton Shrimp Disease) were performed. The amplified products (440 bp approximately) confirm the presence of Perezia sp. microsporidia in analyzed shrimps.

The high degree of damage caused by this parasite through tissue invasion is an important factor to consider to improve biosecurity, diagnosis and health strategies for aquaculture and fisheries.