Serological evidence of arboviruses and coccidia infecting horses in the Amazonian region of Brazil.
Authors: Gomes Fábio Alves, Jansen Ana Maria, Machado Rosângela Zacarias, Jesus Pena Hilda Fátima, Fumagalli Marcílio Jorge, Silva Angélica, Alves Bruna Farias, Roque André Luiz Rodrigues, Moraes Figueiredo Luiz Tadeu
Journal: PloS one
Summary
Brazilian Amazonian horses frequently encounter multiple neurotropic pathogens that can trigger neurological disease, yet their epidemiological significance remains poorly characterised in the region. Researchers screened 213 blood samples from 29 farms across three municipalities using serological methods tailored to detect arboviruses (St Louis Encephalitis virus, West Nile virus, Mayaro virus) and protozoans (Sarcocystis neurona, Toxoplasma gondii, Neospora spp.), applying standardised diagnostic criteria including indirect fluorescent antibody testing and plaque reduction neutralisation assays. Sarcocystis neurona demonstrated the highest protozoan prevalence at 40.3%, whilst St Louis Encephalitis virus infection was remarkably prevalent in arbovirus-positive horses (92%), with 18% of the population showing concurrent infection by S. neurona and at least one arbovirus. Critically, co-infection patterns—particularly SLEV with S. neurona—were documented in horses with resolved neurological signs, suggesting these agents warrant consideration during differential diagnosis of equine neurological cases in South Roraima, though causality between seropositivity and clinical disease requires further investigation. For practitioners managing horses presenting with neurological signs in Amazonian regions, this work underscores the need for comprehensive serological screening protocols and highlights that polyparasitism rather than single-agent disease may be the epidemiological norm in this setting.
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Practical Takeaways
- •In the Amazonian region of Brazil, Sarcocystis neurona and Saint Louis Encephalitis virus should be primary differential diagnoses when investigating neurological disease in horses, as S. neurona alone affects 40% of horses and co-infections are common (18%)
- •Serological testing protocols using IFAT for protozoans and ELISA with PRNT confirmation for arboviruses can effectively identify these neurotrophic pathogens in regional horse populations
- •Horses that have clinically recovered from neurological signs may still test positive for SLEV and S. neurona co-infection, suggesting these infections warrant investigation even in horses with resolving symptoms
Key Findings
- •Sarcocystis neurona was the most prevalent protozoan infection at 40.3% (86/213 horses) in Amazonian Brazilian horses
- •Saint Louis Encephalitis virus was detected in 92% of arbovirus-positive samples (76/83), West Nile virus in 43% (6/14), and Mayaro virus in 33% (16/48)
- •Co-infection with S. neurona and arboviruses occurred in 18% of horses (39/213), particularly with SLEV and/or MAYV
- •Trypanosoma evansi was not detected in any of the 213 samples, and Toxoplasma gondii/Neospora spp. infections were rare (2 cases)