Hepatozoon caimani in Caiman crocodilus yacare (Crocodylia, Alligatoridae) from North Pantanal, Brazil / Hepatozoon caimani em Caiman crocodilus yacare (Crocodylia, Alligatoridae) do Norte do Pantanal, Brasil

Abstract Hepatozoon species are the most common intracellular hemoparasite found in reptiles. Hepatozoon caimani, whose vectors are Culex mosquitoes, has been detected in a high prevalence among caimans in Brazil by blood smears examinations. The present work aimed to detect and characterize the Hepatozoon spp. found in 33 caimans (24 free-ranging and 9 captive; 28 males and 5 females) (Caiman crocodilus yacare) sampled at Poconé, North Pantanal, state of Mato Grosso, Brazil, using blood smears examinations and molecular techniques. Hepatozoon spp.-gametocytes were found in 70.8% (17/24) and 88.8% (8/9) of blood smears from free-ranging and captive caimans, respectively. Hepatozoon spp. 18S rRNA DNA was found in 79.2% (19/24) and 88.8% (8/9) of free-ranging and captive caimans, respectively. Comparative analysis of parasitized and non-parasitized erythrocytes showed that all analyzed features were significantly different (P<0.05) for both linear and area dimensions. Phylogenetic analysis based on 18S rRNA sequences grouped the Hepatozoon spp. sequences detected in the present study together with H. caimani, recently detected in caimans in southern Pantanal.

Resumo Espécies do gênero Hepatozoon são os hemoparasitas intracelulares mais comumente encontrados em répteis. Hepatozoon caimani, cujos vetores são mosquitos do gênero Culex sp., têm sido detectados em uma alta prevalência entre jacarés no Brasil, por meio da análise de esfregaços sanguíneos. O presente estudo objetivou detectar e caracterizar parasitas do gênero Hepatozoon spp. em 33 jacarés (24 de vida-livre e 9 de cativeiro; 28 machos e 5 fêmeas) (Caiman crocodilus yacare) amostrados em Poconé, região norte do Pantanal, estado do Mato Grosso, Brasil, por meio da análise de esfregaços sanguíneos e técnicas moleculares. Gametócitos de Hepatozoon spp. foram encontrados em 70,8% (17/24) e em 88,8% (8/9) dos esfregaços sanguíneos de jacarés de via-livre e cativeiro, respectivamente. 18S rRNA DNA de Hepatozoon spp. foi detectado em 79,2% (19/24) e 88,8% (8/9) das amostras de sangue de jacarés de vida-livre e cativeiro, respectivamente. A análise comparativa de eritrócitos parasitados e não parasitados mostrou diferença significativa (P<0,05) em todas as variáveis lineares e de área analisadas. A análise filogenética baseada em sequências de DNA do 18S rRNA agrupou as sequências de Hepatozoon spp. detectadas no presente estudo juntamente com aquelas de H. caimani, recentemente detectadas em jacarés do Pantanal do Mato Grosso do Sul.

Neutralising antibodies for Mayaro virus in Pantanal, Brazil

The Pantanal hosts diverse wildlife species and therefore is a hotspot for arbovirus studies in South America. A serosurvey for Mayaro virus (MAYV), eastern (EEEV), western (WEEV) and Venezuelan (VEEV) equine encephalitis viruses was conducted with 237 sheep, 87 free-ranging caimans and 748 equids, including 37 collected from a ranch where a neurologic disorder outbreak had been recently reported. Sera were tested for specific viral antibodies using plaque-reduction neutralisation test. From a total of 748 equids, of which 264 were immunised with vaccine composed of EEEV and WEEV and 484 had no history of immunisation, 10 (1.3%) were seropositive for MAYV and two (0.3%) for VEEV using criteria of a ≥ 4-fold antibody titre difference. Among the 484 equids without history of immunisation, 48 (9.9%) were seropositive for EEEV and four (0.8%) for WEEV using the same criteria. Among the sheep, five were sero- positive for equine encephalitis alphaviruses, with one (0.4%) for EEEV, one (0.4%) for WEEV and three (1.3%) for VEEV. Regarding free-ranging caimans, one (1.1%) and three (3.4%), respectively, had low titres for neutralising antibodies to VEEV and undetermined alphaviruses. The neurological disorder outbreak could not be linked to the alphaviruses tested. Our findings represent strong evidence that MAYV and all equine encephalitis alphaviruses circulated in the Pantanal.

Neutralising antibodies for West Nile virus in horses from Brazilian Pantanal

Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for WNV and its most closely-related flaviviruses that circulate in Brazil to confirm the detection of specific virus-neutralising antibodies. Of the 93 (55.4 percent) blocking ELISA-seropositive horse serum samples, five (3 percent) were seropositive for WNV, nine (5.4 percent) were seropositive for St. Louis encephalitis virus, 18 (10.7 percent) were seropositive for Ilheus virus, three (1.8 percent) were seropositive for Cacipacore virus and none were seropositive for Rocio virus using PRNT90, with a criteria of > four-fold antibody titre difference. All caimans were negative for flaviviruses-specific antibodies using the blocking ELISA. No virus genome was detected from caiman blood or mosquito samples. The present study is the first report of confirmed serological evidence of WNV activity in Brazil.