Cryptosporidium geckonae n. sp. (Apicomplexa: Cryptosporidiidae) in geckos

Cryptosporidium is a globally prevalent parasite that infects the gastrointestinal tract of a large number of vertebrates. The Cryptosporidium sp. lizard genotype is found almost exclusively in geckos but has also been detected in a corn snake. In this study, the biology and genetic variability of the lizard genotype were investigated.

The genetic variability of the Cryptosporidium sp. lizard genotype was analysed by polymerase chain reaction (PCR) and Sanger sequencing of the SSU rRNA, actin, HSP70 and COWP genes. Its biological characteristics, including oocyst size, tissue tropism and associated pathology, were investigated using light microscopy, electron microscopy and histological techniques. Experimental infections were performed to assess host specificity and infectivity.

Phylogenetic analysis of the target genes confirmed that the Cryptosporidium sp. lizard genotype is genetically distinct from other Cryptosporidium species. Experimental infections showed that chickens, mice and corn snakes were not susceptible to this genotype, as no infection was detected. In contrast, leopard geckos began to excrete oocysts between 6 and 8 days post-infection, although they showed no clinical symptoms. Excretion of oocysts continued for over 200 days. Oocysts isolated from naturally infected leopard and smooth knob-tailed geckos were morphometrically identical to those from experimentally infected leopard geckos and measured 5.89 × 4.79 μm. The parasite mainly colonised the stomach, where the highest intensity of infection was observed, but was also found throughout the intestine and in the lungs.

Due to the distinct genetic differences, host range and tissue tropism, we propose the name Cryptosporidium geckonae n. sp. for this organism, which was previously referred to as Cryptosporidium sp. lizard genotype.