A participatory surveillance of marsh deer (Blastocerus dichotomus) morbidity and mortality in Argentina: first results.

BACKGROUND: In an era of unprecedented socio-ecological changes, managing wildlife health demands high-quality data collection and the engagement of local communities. Blastocerus dichotomus, the largest South American deer, is Vulnerable to extinction mainly due to habitat loss. Diseases have been recognised as a potential threat, and winter mortality has been historically described in marsh deer populations from Argentina. Field difficulties have, however, prevented in-depth studies of their health status. RESULTS: Between May 2014 and April 2017, we investigated marsh deer morbidity and mortality in the two largest populations in Argentina. We collected data by means of a passive surveillance system that involved a network of researchers, field partners (veterinarians, park rangers, and local community), and decision makers. We sampled marsh deer during as well as outside mortality events. A total of 44 marsh deer with different body condition scores were evaluated. We obtained haematology and biochemistry values from animals with good body condition score. Marsh deer with poor body condition had a high burden of the ticks Amblyomma triste and Rhipicephalus microplus. Vector-borne agents such as Theileria cervi, Trypanosoma theileri, Trypanosoma evansi, Ehrlichia chaffeensis, Anaplasma platys, Anaplasma odocoilei, Anaplasma marginale, and Candidatus Anaplasma boleense were also found. Haemonchus spp., Ostertagia spp., and Trichostrongylus spp. were the most frequent gastrointestinal parasites in deer with poor body condition. A Multiple Correspondence Analysis reinforced a possible association of winter period with lower body score condition, high tick loads, infection with E. chaffeensis, and presence of harmful gastrointestinal parasites. CONCLUSIONS: Our approach allowed the establishment of a participatory surveillance network of marsh deer morbidity and mortality in Argentina. We report and analyse the first data obtained opportunistically within the framework of this network, providing information on the infectious and parasitic agents in marsh deer populations. The occurrence of Fasciola hepatica and Leptospira interrogans serovar pyrogenes is reported for the first time in wild marsh deer from Argentina. Our data will be useful to improve the interpretation of future mortality events. The field implementation of a surveillance network is key to a holistic approach to wildlife diseases.

Identification of a new Sarcocystis sp. in marsh deer (Blastocerus dichotomus) from wetlands of Argentina.

The marsh deer (Blastocerus dichotomus) is the largest South American native deer species and is listed as "Vulnerable" by IUCN due to the population reduction. As part of a conservation and disease surveillance program, muscle samples from 14 marsh deer found dead in 2016 and 2017 in northeast Argentina were obtained at necropsy. Samples from each animal were processed as pooled muscles (heart, diaphragm, tongue and hindlimb) by homogenization and direct microscopical observation to detect intracellular Sarcocystis spp. cysts. Sarcocysts were observed in six samples, and several cysts recovered from two samples were processed by transmission electron microscopy. The cysts were thin-walled and showed a cyst-wall ultrastructure with ribbon-like protrusions similar to other species using cervids as intermediate host and canids as definitive hosts. Genomic DNA from individual sarcocysts from three marsh deer were successfully amplified by PCR of 18S rRNA and COI gene fragments and further sequenced. Sequence comparison revealed a 99.3-100% identity among them and only 93.7-96.6% and 88.8-89.7% identity at 18S rRNA and COI markers, respectively, with other Sarcocystis spp. Despite morphological similarities, the high sequence divergence at 18S rRNA and COI fragments allowed the assumption that Sarcocystis sp. from marsh deer is a different species from others using cervids as intermediate hosts. Therefore, we propose the name Sarcocystis blastoceris n. sp. for the species infecting marsh deer.

Evidence of Ehrlichia chaffeensis in Argentina through molecular detection in marsh deer (Blastocerus dichotomus).

Vector-borne pathogens are responsible for serious emerging diseases and have been widely described in wildlife. Ehrlichia chaffeensis causes the zoonotic "monocytic ehrlichiosis" in humans, is transmitted by the tick Amblyomma americanum and its reservoir host is the white-tailed deer (Odocoileus virginianus) in North America. Little is known about the native reservoir and the tick vectors involved in the transmission cycle in South America. We report here the detection of E. chaffeensis in a study on marsh deer (Blastocerus dichotomus) mortality in Argentina, in different time periods between 2007 and 2016. Four deer, from two distinct populations, were positive for E. chaffeensis through molecular methods. Additionally, the variable-length PCR target (VLPT) region of positive samples was genotyped. Our results provide the first evidence of E. chaffeensis in autochthonous Cervidae from Argentina, contributing to uncover the distribution of this tick-borne infection in South America.

Morfologia da língua do cervo do pantanal (Blastocerus dichotomus) / Morphology of the tongue of the Marsh deer (Blastocerus dichotomus)

Objetivou-se descrever a morfologia da língua do cervo do pantanal (Blastocerus dichotomus), o maior cervídeo da fauna brasileira, pois poucas são as informações detalhadas sobre sua morfologia. Línguas e fragmentos linguais de oito cervos do pantanal, adultos, provenientes do Projeto Cervo-do-Pantanal de Porto Primavera foram analisados quanto aos seus aspectos macroscópicos e à microscopia de luz. A língua do cervo do pantanal ocupa grande parte da cavidade oral, onde a raiz e o corpo estão fixados caudalmente pelo osso hióide e, em sua porção média, pelo frênulo lingual; seu ápice, achatado e plano é livre; apresenta torus lingual pouco proeminente, não havendo delimitação da fossa lingual. Na superfície dorsal encontram-se as seguintes papilas: filiformes, cônicas, lenticulares, fungiformes e valadas. Histologicamente verificou-se que a mucosa reveste-se de epitélio estratificado pavimentoso queratinizado, a lâmina própria constitui-se de tecido conjuntivo, rico em fibras colágenas dispostas em várias direções, onde se verifica abundante vascularização, além de acúmulo de tecido linfático.

The aim was to describe the morphology of the tongue of the Marsh deer (Blastocerus dichotomus), the largest deer of the Brazilian fauna, since there is little detailed information on their morphology. Tongues of eight adult Marsh deers, belonging to Projeto cervo-do-pantanal de Porto Primavera were analyzed for their macroscopic aspects and by light microscopy. The Marsh deer tongue occupies most of the oral cavity, where the root and body are fixed caudally by the hyoid bone, and in its middle portion by the frenulum linguae; its free apex is flat and plane, has little prominent torus lingae and there is no demarcation of fossa linguae. The lateral and ventral surfaces are covered by a thin mucosa; however the dorsal surface is covered by thick mucosa, although soft. On the dorsal surface are the papillae: filiform, conical, lenticular, fungiform and vallate. Histologically was found that the mucosa has a stratified squamous epithelium, the lamina propria consists of connective tissue rich in collagen fibers arranged in several directions, where there is abundant vascularization and accumulation of lymphoid tissue.

Transferability of microsatellite loci from Cervidae species to the endangered Brazilian marsh deer, Blastocerus dichotomus

Blastocerus dichotomus, the marsh deer, is the largest Brazilian Cervidae species. The species is endangered because of hunting and loss of its natural habitat, i.e., flood plain areas, because of hydroelectric power station construction and agricultural land expansion. In the present study, we tested 38 microsatellite loci from four Cervidae species: Odocoileus virginianus (7), Rangifer tarandus (17), Capreolus capreolus (7), and Mazama bororo (7). Eleven loci showed clear amplification, opening a new perspective for the generation of fundamental population genetic data for devising conservation strategies for B. dichotomus.