Serological evidence of arboviruses and coccidia infecting horses in the Amazonian region of Brazil

Effect of refrigeration, room temperature, and processing time on serum immunofluorescent antibody titers for Sarcocystis neurona

BACKGROUND

Evaluating antibody titers for Sarcocystis neurona for the diagnosis of equine protozoal myeloencephalitis from serum samples is a common practice. However, ensuring timely and proper refrigeration is not always possible.

OBJECTIVES

To evaluate immunofluorescent antibody (IFA) titers for S. neurona from serum samples stored at room temperature and 4°C.

SAMPLES

Twenty-two serum samples.

METHODS

Prospective longitudinal study. Two serum aliquots of 1 mL each were stored at room temperature (20-23.3°C) and 4°C. The unrefrigerated aliquot was immediately tested for IFA titers. Both aliquots were retested on Days 5 and 10 after collection. A paired t test was used to compare IFA titers at different time points.

RESULTS

There was no significant difference between IFA titers from baseline with those stored at room temperature at Days 5 (P = .741, 95% CI [-56.83, 78.65]), 10 (P = .677, 95% CI [-50.01, 75.46]), and between 5 and 10 days (P = 0.949, 95% CI [-57.50, 61.14]). There was no significant difference from baseline with those stored at 4°C for Days 5 (P = .964, 95% CI [-81.81, 85.45]), 10 (P = 0.573, 95% CI [-109.4, 62.15]), and between 5 and 10 days (P = .5, 95% CI [-102.6, 51.67]). There was no statistical difference between samples stored at room temperature and 4°C (P = .688, CI [-55.51, 37.33]) on Days 5 and 10 (P = .104, CI [-80.8, 8.07]).

CONCLUSIONS AND CLINICAL IMPORTANCE

Immunofluorescent antibody test titers for S. neurona are stable for up to 10 days at room temperature and 4°C.

Detection and prevalence of a novel Bandavirus related to Guertu virus in Amblyomma gemma ticks and human populations in Isiolo County, Kenya

INTRODUCTION

Emerging tick-borne viruses of medical and veterinary importance are increasingly being reported globally. This resurgence emphasizes the need for sustained surveillance to provide insights into tick-borne viral diversity and associated potential public health risks. We report on a virus tentatively designated Kinna virus (KIV) in the family Phenuiviridae and genus Bandavirus. The virus was isolated from a pool of Amblyomma gemma ticks from Kinna in Isiolo County, Kenya. High throughput sequencing of the virus isolate revealed close relatedness to the Guertu virus. The virus genome is consistent with the described genomes of other members of the genus Bandavirus, with nucleotides lengths of 6403, 3332 and 1752 in the Large (L), Medium (M) and Small (S) segments respectively. Phylogenetic analysis showed that the virus clustered with Guertu virus although it formed a distinct and well supported branch. The RdRp amino acid sequence had a 93.3% identity to that of Guertu virus, an indication that the virus is possibly novel. Neutralizing antibodies were detected in 125 (38.6%, 95% CI 33.3-44.1%) of the human sera from the communities in this region. In vivo experiments showed that the virus was lethal to mice with death occurring 6-9 days post-infection. The virus infected mammalian cells (Vero cells) but had reduced infectivity in the mosquito cell line (C636) tested.

CONCLUSION

Isolation of this novel virus with the potential to cause disease in human and animal populations necessitates the need to evaluate its public health significance and contribution to disease burden in the affected regions. This also points to the need for continuous monitoring of vector and human populations in high-risk ecosystems to update pathogen diversity.

Reactivity against Sarcocystis neurona and Sarcocystis falcatula-like in horses from Southeastern and Midwestern Brazil

Equine protozoal myeloencephalitis (EPM) is a neurological disease caused by Sarcocystis neurona. Immunofluorescence antibody tests (IFATs) have been widely used to identify exposure of horses to S. neurona in Brazil. Here we used IFAT to search for IgG antibodies against Sarcocystis falcatula-like (Dal-CG23) and S. neurona (SN138) in sera from 342 horses sampled in Campo Grande, Mato Grosso do Sul state (Midwestern), and São Paulo, São Paulo state (Southeastern), Brazil. The 1:25 cutoff value was chosen to maximize sensitivity of the test. IgG antibodies against S. neurona were detected in 239 horses (69.88%), whereas IgG antibodies against S. falcatula-like were detected in 177 horses (51.75%). Sera from 132 horses (38.59%) reacted against both isolates. Absence of reactivity was evidenced in 58/342 horses (16.95%). The lower cutoff used, and the presence of opossums infected with S. falcatula-like and Sarcocystis spp. in the regions where the horses were sampled, might justify the high seroprevalence observed here. Owing to the similarity among antigens targeted in immunoassays, reports on S. neurona-seropositive horses in Brazil may also derive from the exposure of horses to other Sarcocystis species. The role of other Sarcocystis species in causing neurological diseases in horses in Brazil remains unclear.

Serological Evidence of Arboviruses in Horses During West Nile Fever Monitoring Surveillance in Southeastern Brazil

Many human arboviruses are also pathogenic for horses, and some of these have emerged recently. A descriptive cross-sectional observational study was conducted to assess the prevalence of West Nile virus (WNV) and other arboviruses among 77 horses on the rural properties of the Espirito Santo state, Brazil. Serum samples were screened for arbovirus-reactive antibodies using the hemagglutination inhibition technique and subsequently a plaque reduction neutralization test for the confirmation of exposure from sera was used to detect heterotypic immune reactions. Overall, the total antibodies against at least one arbovirus of Alphavirus, Flavivirus, and Orthobunyavirus genera were detected in 39 (50.6%) animals. The antibodies to Phlebovirus were not detected in any sample. When the 24 WNV hemagglutination inhibition (HI)-positive samples were tested by the plaque-reduction neutralization test 90%, 9 (32.1%) were positive for WNV antibodies and 14 (50%) for Saint Louis encephalitis virus. Our findings indicate that the region provides ideal conditions for the emergence of arboviruses, reinforcing the need for further surveillance of mosquito-transmitted diseases in domestic animals.

Invited review: Sarcocystis neurona, Neospora spp. and Toxoplasma gondii infections in horses and equine protozoal myeloencephalitis (EPM): five decades of personal experience, perspectives, and update

Sarcocystis neurona, Neospora spp. and Toxoplasma gondii are related protozoans; they were considered the same parasite until 1970s. Two of these parasites, S. neurona and Neospora spp. are associated with a neurological syndrome in horses, called equine protozoal myeloencephalitis (EPM). The diagnosis and treatment of EPM are difficult. Most cases of EPM are related to S. neurona while only a few are due to Neospora spp. infections. There are two species of Neospora, Neospora caninum that has a wide host range and Neospora hughesi that has been found only in horses. Currently, T. gondii is not considered as a cause of EPM in horses, although it causes neurological illness in many other hosts, including humans. The present review provides an update on history, life cycle, diagnosis and treatment of these three infections in horses.

A systematic review and meta-analysis of the potential non-human animal reservoirs and arthropod vectors of the Mayaro virus

Improving our understanding of Mayaro virus (MAYV) ecology is critical to guide surveillance and risk assessment. We conducted a PRISMA-adherent systematic review of the published and grey literature to identify potential arthropod vectors and non-human animal reservoirs of MAYV. We searched PubMed/MEDLINE, Embase, Web of Science, SciELO and grey-literature sources including PAHO databases and dissertation repositories. Studies were included if they assessed MAYV virological/immunological measured occurrence in field-caught, domestic, or sentinel animals or in field-caught arthropods. We conducted an animal seroprevalence meta-analysis using a random effects model. We compiled granular georeferenced maps of non-human MAYV occurrence and graded the quality of the studies using a customized framework. Overall, 57 studies were eligible out of 1523 screened, published between the years 1961 and 2020. Seventeen studies reported MAYV positivity in wild mammals, birds, or reptiles and five studies reported MAYV positivity in domestic animals. MAYV positivity was reported in 12 orders of wild-caught vertebrates, most frequently in the orders Charadriiformes and Primate. Sixteen studies detected MAYV in wild-caught mosquito genera including Haemagogus, Aedes, Culex, Psorophora, Coquillettidia, and Sabethes. Vertebrate animals or arthropods with MAYV were detected in Brazil, Panama, Peru, French Guiana, Colombia, Trinidad, Venezuela, Argentina, and Paraguay. Among non-human vertebrates, the Primate order had the highest pooled seroprevalence at 13.1% (95% CI: 4.3-25.1%). From the three most studied primate genera we found the highest seroprevalence was in Alouatta (32.2%, 95% CI: 0.0-79.2%), followed by Callithrix (17.8%, 95% CI: 8.6-28.5%), and Cebus/Sapajus (3.7%, 95% CI: 0.0-11.1%). We further found that MAYV occurs in a wide range of vectors beyond Haemagogus spp. The quality of evidence behind these findings was variable and prompts calls for standardization of reporting of arbovirus occurrence. These findings support further risk emergence prediction, guide field surveillance efforts, and prompt further in-vivo studies to better define the ecological drivers of MAYV maintenance and potential for emergence.

Emergent Arboviruses: A Review About Mayaro virus and Oropouche orthobunyavirus

Arthropod-borne viruses have a significant impact on public health worldwide, and their (re) emergence put aside the importance of other circulating arboviruses. Therefore, this scoping review aims to identify and characterize the literature produced in recent years, focusing on aspects of two arboviruses: Mayaro virus and Oropouche orthobunyavirus. The Mayaro and Oropouche viruses were isolated for the first time in Trinidad and Tobago in 1954 and 1955, respectively, and have more recently caused numerous outbreaks. In addition, they have been incriminated as candidate diseases for human epidemics. These viruses have been drawing the attention of public health authorities worldwide following recent outbreaks. To determine the global epidemiological profile of these viruses, we used the Dimensions Database, which contains more than 100 million publications. In general, we identified 327 studies published from 1957 to 2020 for Mayaro virus, and 152 studies published from 1961 to 2020 for Oropouche orthobunyavirus. Interestingly, we observed that Mayaro and Oropouche had a significant increase in the number of publications in recent years. Thus, this comprehensive review will be helpful to guide future research based on the identified knowledge gaps.

West Nile Virus in the State of Ceará, Northeast Brazil

In June 2019, a horse with neurological disorder was diagnosed with West Nile virus (WNV) in Boa Viagem, a municipality in the state of Ceará, northeast Brazil. A multi-institutional task force coordinated by the Brazilian Ministry of Health was deployed to the area for case investigation. A total of 513 biological samples from 78 humans, 157 domestic animals and 278 free-ranging wild birds, as well as 853 adult mosquitoes of 22 species were tested for WNV by highly specific serological and/or molecular tests. No active circulation of WNV was detected in vertebrates or mosquitoes by molecular methods. Previous exposure to WNV was confirmed by seroconversion in domestic birds and by the detection of specific neutralizing antibodies in 44% (11/25) of equids, 20.9% (14/67) of domestic birds, 4.7% (13/278) of free-ranging wild birds, 2.6% (2/78) of humans, and 1.5% (1/65) of small ruminants. Results indicate that not only equines but also humans and different species of domestic animals and wild birds were locally exposed to WNV. The detection of neutralizing antibodies for WNV in free-ranging individuals of abundant passerine species suggests that birds commonly found in the region may have been involved as amplifying hosts in local transmission cycles of WNV.

Sarcocystis neurona and related Sarcocystis spp. shed by opossums (Didelphis spp.) in South America

Protozoan parasites of the genus Sarcocystis are obligatory heteroxenous cyst-forming coccidia that infect a wide variety of animals and encompass approximately 200 described species. At least four Sarcocystis spp. (S. falcatula, S. neurona, S. lindsayi and S. speeri) use opossums (Didelphis spp.) as definitive hosts, and two of them, S. neurona and S. falcatula, are known to cause disease in horses and birds, respectively. Opossums are restricted to the Americas, but their distribution in the Americas is heterogeneous. Five Didelphis spp. are distributed in South America (D. aurita, D. albiventris, D. marsupialis, D. imperfecta and D. pernigra) whereas just one opossum species (D. virginiana) is found in North America. Studies conducted in the last decades show that Sarcocystis spp., derived from South American Didelphis spp., have biological and genetic differences in relation to Sarcocystis spp. shed by the North American opossum D. virginiana. The aim of this review was to address the peculiar scenario of Sarcocystis species shed by South American opossums, with a special focus on diagnosis, epidemiology, and animal infections, as well as the genetic characteristics of these parasites.

Larvicidal effect from different Annonaceae species on Culex quinquefasciatus

The recent outbreaks of mosquito-borne diseases highlighted the pivotal importance of mosquito vector control in tropical areas worldwide. Several strategies have been developed to control vector populations and disease transmission in endemic areas. The steps to obtain natural active compounds involve the pre-selection in a biological model and subsequently evaluation on specific models. The present study reports the evaluation of 35 extracts, fractions, and essential oils obtained from five species from the Annonaceae family on Artemia salina and Culex quinquefasciatus. The A. salina results were used as a pre-screening for larvicidal test about mosquitoes. A correlation of biological activity in both bioassays was observed for the hydroethanolic extracts and their respective hexane and chloroform fractions of the leaves of Annona species, except A. nutans. The same correlation was also observed for all tested essential oils and petroleum ether extracts from Duguetia species. It was possible to limit an interval of lethality about A. salina, which has a corresponding range to the larvicidal test against the mosquito. The main components present in D. lanceolata essential oil or enriched fraction were α-selinene, aristolochene, (E)-caryophyllene, and (E)-calamenene. For D. furfuracea, the main components present of the underground parts were (E)-asarone, 2,4,5-trimethoxystyrene, spathulenol, and bicyclogermacrene for aerial parts. The A. salina test could be used as a model for the pre-screening of larvicidal activity.