Encephalitozoon cuniculi genotype III evinces a resistance to Albendazole treatment in both immunodeficient and immunocompetent mice.

Out of four genotypes of Encephalitozoon cuniculi, E. cuniculi genotype II is considered to be a parasite that occurs in many host species in a latent asymptomatic form, whereas E. cuniculi genotype III seems to be more aggressive and infections caused by this strain can lead to the death of even immunocompetent hosts.Although Albendazole has been considered suitable for treatment of Encephalitozoon species, its failure in control of E. cuniculi genotype III infection has been reported. This study determined the effect of 100x recommended daily dose of Albendazole on Encephalitozoon cuniculi genotype III course of infection in immunocompetent and immunodefficient mice and compared the results with experiments performed with lower dose of Albendazole and E. cuniculi genotype II.The administration of regular dose of Abendazole during the acute phase of infection reduced the number of affected organs in all strains of mice and absolute counts of spores in screened organs. However, the effect on genotype III was minor. Surprisingly, no substantial effect was recorded by using 100x dose of Albendazole with only larger reduction in number of affected organs and absolute counts of spores in all mice strains implying variation in Albendazole resistance between these Encephalitozoon cuniculi genotypes.These results imply that differences in the course of infection and the response to treatment depend not only on immunological status of the host, but also on the genotype causing the infection. Understanding how microsporidia survive in hosts despite targeted anti-microsporidial treatment could significantly contribute to research related to human health.