Ticks and accompanying pathogens of domestic and wild animals of Kerala, South India.

The objective of the present study was to detect the chosen nucleotide DNA or RNA sequences of the pathogens in ticks of domestic and wild animals of Kerala, South India based on molecular techniques. Among 602 ticks collected, 413 were from bovines (cattle and buffalo), 26 from goats, 101 from dogs and 62 from wild animals. Amblyomma integrum, Am. gervaisi, Dermacentor auratus, Haemaphysalis bispinosa, Ha. intermedia, Ha. shimoga, Ha. spinigera, Rhipicephalus annulatus, Rh. microplus, Rh. haemaphysaloides and Rh. sanguineus s.l. were identified from various domestic and wild animals of Kerala. The cDNA synthesized from the RNA isolated from fully or partially engorged adult female/nymphal ticks was used as template for the specific polymerase chain reactions (PCR). Out of 602 ticks examined, nucleotide sequences of pathogens were detected in 28 ticks (4.65%). The nucleotide sequences of tick-borne pathogens like Theileria orientalis, Babesia vogeli, Hepatozoon canis, Anaplasma marginale, An. bovis, Rickettsia sp. closely related to Ri. raoultii, Ri. massiliae, Ri. africae and Ri. slovaca were detected. The identification of the previously unreported nucleotide sequences of rickettsial pathogens from India is of particular interest due to their zoonotic significance. The phylogenetic analysis of the major piroplasm surface protein (MPSP) gene of T. orientalis amplified from Rh. annulatus ticks revealed that they were genetically close to type 7, which belong to the highly pathogenic Ikeda group.

Whether Dirofilaria repens parasites from South India belong to zoonotic Candidatus Dirofilaria hongkongensis (Dirofilaria sp. hongkongensis)?

The canine and zoonotic dirofilarioses are arthropod-borne parasitic infections caused by nematodes of the genus Dirofilaria, infecting canines, felines and humans throughout the world. Dirofilaria repens was considered as the most common cause of human dirofilariosis in Kerala. In the present study, molecular characterization of Dirofilaria isolates causing dirofilariosis in humans, dogs and jackal from Kerala, South India was undertaken by performing sequence and phylogenetic analysis based on cytochrome oxidase subunit I (COI) gene. The live worms from swellings/ nodules in subconjunctiva or subcutaneous tissue or scrotum were recovered from humans (n = 3), dogs (n = 4) and one jackal. The PCRs targeting a repetitive fragment, 18S rRNA and COI genes yielded products of ~246 bp, ~875 bp and ~350 bp respectively in all the samples. The sequence analysis of 18S rRNA gene revealed the closest identity (98 to 99%) with an already published sequence of D. repens isolated from a human in Japan. However, based on the sequence and phylogenetic analysis of partial sequences of COI gene, the Dirofilaria infecting both animals (dogs, jackal) and humans native to Kerala, South India were identified as genetically conserved and closely related to Dirofilaria sp. hongkongensis. Hence, the results of the present study suggested the existence of Candidatus Dirofilaria hongkongensis (Dirofilaria sp. hongkongensis) in Kerala, South India causing zoonotic filariosis in canines and humans.