New Babesia parasite causes severe anemia in domestic cats

Abstract

BACKGROUND: Babesiosis is a tick-borne infection caused by piroplasmid protozoa and associated with anemia and severe disease in humans, domestic animals and wildlife. Domestic cats are infected by at least six Babesia spp. that cause clinical disease. METHODS: Infection with a piroplasmid species was detected by microscopy of stained blood smears in three sick cats from Israel. Genetic characterization of the piroplasmid was performed by PCR amplification of the 18S rRNA, cytochorme B (CytB) and heat shock protein 70 (HSP70) genes and the internal transcribed spacer (ITS) locus, DNA sequencing and phylogenetic analysis. In addition, Haemaphysalis adleri ticks collected from two cats were analyzed by PCR for piroplasmids. RESULTS: The infected cats presented with anemia and thrombocytopenia (3/3), fever (2/3) and icterus (1/3). Comparison of gene and loci sequences found 99-100% identity between sequences amplified from different cats and ticks. Constructed phylogenetic trees and DNA sequence comparisons demonstrated a previously undescribed Babesia sp. belonging to the Babesia sensu stricto (clade X). The piroplasm forms detected included pear-shaped merozoite and round-to-oval trophozoite stages with average sizes larger than those of Babesia felis, B. leo and B. lengau and smaller than canine Babesia s.s. spp. Four of 11 H. adleri adult ticks analyzed from cat # 3 were PCR positive for Babesia sp. with a DNA sequence identical to that found in the cats. Of these, two ticks were PCR positive in their salivary glands, suggesting that the parasite reached these glands and could possibly be transmitted by H. adleri. CONCLUSIONS: This study describes genetic and morphological findings of a new Babesia sp. which we propose to name Babesia galileei sp. nov. after the Galilee region in northern Israel where two of the infected cats originated from. The salivary gland PCR suggests that this Babesia sp. may be transmitted by H. adleri. However, incriminating this tick sp. as the vector of B. galilee sp. nov. would require further studies.