Natural Canine Distemper Virus Infection in Linnaeus's 2-Toed Sloths (Choloepus didactylus).

An outbreak of canine distemper virus in a private zoo in eastern Tennessee in July 2016 led to fatal clinical disease in 5 adult, wild-caught Linnaeus's 2-toed sloths (Choloepus didactylus). Clinical signs included hyporexia, lethargy, mucopurulent nasal discharge, and oral and facial ulcers. At necropsy, affected animals had crusts and ulcers on the lips, nose, tongue, and oral cavity. Microscopically, all sloths had widespread, random, hepatic necrosis; lymphoid depletion; and bronchointerstitial pneumonia. The central nervous system did not contain gross or histopathologic lesions in any of the 5 sloths, although immunoreactivity for viral antigen was present within vessel walls. Epithelial cells and histiocytes within numerous organs contained intranuclear and intracytoplasmic inclusions and occasional syncytial cells. Canine distemper virus was confirmed with immunohistochemistry and virus isolation. Viral sequencing identified the novel American-4 strain prevalent in eastern Tennessee wildlife. This is the first pathologic characterization of canine distemper virus infection in sloths (family Choloepodidae, order Pilosa) and emphasizes the significant morbidity and mortality in this species.

Sloths host Anhanga virus-related phleboviruses across large distances in time and space.

Sloths are genetically and physiologically divergent mammals. Phleboviruses are major arthropod-borne viruses (arboviruses) causing disease in humans and other animals globally. Sloths host arboviruses, but virus detections are scarce. A phlebovirus termed Anhanga virus (ANHV) was isolated from a Brazilian Linnaeus's two-toed sloth (Choloepus didactylus) in 1962. Here, we investigated the presence of phleboviruses in sera sampled in 2014 from 74 Hoffmann's two-toed (Choloepus hoffmanni, n = 65) and three-toed (Bradypus variegatus, n = 9) sloths in Costa Rica by broadly reactive RT-PCR. A clinically healthy adult Hoffmann's two-toed sloth was infected with a phlebovirus. Viral load in this animal was high at 8.5 × 107  RNA copies/ml. The full coding sequence of the virus was determined by deep sequencing. Phylogenetic analyses and sequence distance comparisons revealed that the new sloth virus, likely representing a new phlebovirus species, provisionally named Penshurt virus (PEHV), was most closely related to ANHV, with amino acid identities of 93.1%, 84.6%, 94.7% and 89.0% in the translated L, M, N and NSs genes, respectively. Significantly more non-synonymous mutations relative to ANHV occurred in the M gene encoding the viral glycoproteins and in the NSs gene encoding a putative interferon antagonist compared to L and N genes. This was compatible with viral adaptation to different sloth species and with micro-evolutionary processes associated with immune evasion during the genealogy of sloth-associated phleboviruses. However, gene-wide mean dN/dS ratios were low at 0.02-0.15 and no sites showed significant evidence for positive selection, pointing to comparable selection pressures within sloth-associated viruses and genetically related phleboviruses infecting hosts other than sloths. The detection of a new phlebovirus closely-related to ANHV, in sloths from Costa Rica fifty years after and more than 3,000 km away from the isolation of ANHV confirmed the host associations of ANHV-related phleboviruses with the two extant species of two-toed sloths.

Surveillance of Arboviruses in Primates and Sloths in the Atlantic Forest, Bahia, Brazil.

From 2006 through 2014, we conducted seroepidemiological surveys on non-human primates and sloths to investigate the possible circulation of arboviruses in Bahia Atlantic Forest, Brazil. We collected a total of 196 samples from 103 Leontopithecus chrysomelas, 7 Sapajus xanthosternos, 22 Bradypus torquatus and 7 Bradypus variegatus. Serum samples were tested using neutralization test and hemagglutination inhibition test to detect total antibodies against 26 different arboviruses. The overall prevalence of arboviruses was 36.6% (51/139), with the genus Flavivirus having the highest prevalence (33.1%; 46/139), followed by Phlebovirus (5.0%; 7/139), Orthobunyavirus (4.3%; 6/139) and Alphavirus (0.7%; 1/139). Monotypic reactions suggest that the wild animals were exposed naturally to at least twelve arboviruses. Added results from the neutralization test, animals were exposed to thirteen arboviruses. Most of these viruses are maintained in transmission cycles independent of human hosts, although antibodies against dengue virus serotypes 1, 2 and 3 were found in this study. To our knowledge, this is the first study reporting exposure to arboviruses in L. chrysomelas, S. xanthosternos and B. torquatus. Our results also highlight that the Southern Bahia Atlantic Forest has a variety of vertebrate hosts and potential vectors, which may support the emergence or re-emergence of arboviruses, including those pathogenic to humans.

Oropouche Virus: Clinical, Epidemiological, and Molecular Aspects of a Neglected Orthobunyavirus.

AbstractOropouche virus (OROV) is an important cause of arboviral illness in Latin American countries, more specifically in the Amazon region of Brazil, Venezuela and Peru, as well as in other countries such as Panama. In the past decades, the clinical, epidemiological, pathological, and molecular aspects of OROV have been published and provide the basis for a better understanding of this important human pathogen. Here, we describe the milestones in a comprehensive review of OROV epidemiology, pathogenesis, and molecular biology, including a description of the first isolation of the virus, the outbreaks during the past six decades, clinical aspects of OROV infection, diagnostic methods, genome and genetic traits, evolution, and viral dispersal.

SEROLOGIC RESPONSE TO CANINE DISTEMPER VACCINATION IN CAPTIVE LINNAEUS'S TWO-TOED SLOTHS ( CHOLOEPUS DIDACTYLUS) AFTER A FATAL CANINE DISTEMPER VIRUS OUTBREAK.

Canine distemper virus (CDV) affects many wild and captive, nondomestic species worldwide but has not been previously reported in Xenarthra. Paucity of information on vaccination safety and efficacy presents challenges for disease prevention in captive collections. CDV infections and subsequent mortalities in five captive Linnaeus's two-toed sloths ( Choloepus didactylus) in eastern Tennessee are reported. Clinical signs included oculonasal discharge, oral ulcerations, and diarrhea, and the diagnosis was confirmed by necropsy, histopathology, immunohistochemistry, virus isolation, and polymerase chain reaction. Viral sequencing identified the strain to be consistent with a new CDV lineage currently affecting domestic dogs and wildlife in Tennessee. Seven sloths were examined and vaccinated using a recombinant CDV vaccine on days 0 and 21. Subsequent blood samples showed increased titers in 3/4 sloths. Based on the outbreak and serologic findings postvaccination without adverse effects, the authors recommend recombinant CDV vaccination in sloths exposed to known carriers of CDV.

SEROSURVEY OF SELECTED ARBOVIRAL PATHOGENS IN FREE-RANGING, TWO-TOED SLOTHS (CHOLOEPUS HOFFMANNI) AND THREE-TOED SLOTHS (BRADYPUS VARIEGATUS) IN COSTA RICA, 2005-07.

We screened for antibodies to 16 arboviruses in four populations of free-ranging sloths in Costa Rica. Blood samples were taken from 16 Hoffman's two-toed sloths (HTSs; Choloepus hoffmanni ) and 26 brown-throated sloths (BTSs; Bradypus variegatus ) over a 3-yr period. We used serologic assays to detect antibodies against 10 arboviruses previously described in sloths (St. Louis encephalitis [SLEV], Changuinola, Venezuelan equine encephalitis, Ilheus [ILHV], Oropouche, Mayaro, Utinga, Murutucu, Punta Toro, and vesicular stomatitis [VSV] viruses) and six arboviruses not described in sloths (Rio Grande, West Nile [WNV], eastern equine encephalitis, Piry, Munguba, and La Crosse viruses). Overall, 80% of sloths had detectable antibodies to SLEV, 67% had antibodies to ILHV, 32% to Punta Toro virus, 30% to Changuinola virus, 15% to WNV, 14% to VSV, 11% to Venezuelan equine encephalitis virus, and 10% to Rio Grande virus. No samples had detectable antibodies to the remaining eight viruses. We found a significant increase in prevalence of antibody to VSV in HTSs between 2005 and 2007, and for WNV antibody between 2005 and 2006. We found no significant differences in the prevalences of antibodies to the sampled viruses between the two locations. Antibody prevalences were significantly higher in HTSs than in BTSs for SLEV in 2005. Antibody-positive results for ILHV were likely due to cross-reaction with SLEV. The novel finding of antibodies to Rio Grande virus in sloths could be due to cross-reaction with another phlebovirus. These findings might have implications for land management and domestic animal health. Due to the nature of the study, we could not determine whether sloths could represent amplification hosts for these viruses, or whether they were only exposed and could be used as sentinel species. Further studies are needed to fully characterize arboviral exposure in sloths.

Macroevolution of complex retroviruses.

Retroviruses can leave a "fossil record" in their hosts' genomes in the form of endogenous retroviruses. Foamy viruses, complex retroviruses that infect mammals, have been notably absent from this record. We have found an endogenous foamy virus within the genomes of sloths and show that foamy viruses were infecting mammals more than 100 million years ago and codiverged with their hosts across an entire geological era. Our analysis highlights the role of evolutionary constraint in maintaining viral genome structure and indicates that accessory genes and mammalian mechanisms of innate immunity are the products of macroevolutionary conflict played out over a geological time scale.

Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses.

This is a review of the research undertaken since 1971 on the behavior and physiological ecology of sloths. The animals exhibit numerous fascinating features. Sloth hair is extremely specialized for a wet tropical environment and contains symbiotic algae. Activity shows circadian and seasonal variation. Nutrients derived from the food, particularly in Bradypus, only barely match the requirements for energy expenditure. Sloths are hosts to a fascinating array of commensal and parasitic arthropods and are carriers of various arthropod-borne viruses. Sloths are known reservoirs of the flagellate protozoan which causes leishmaniasis in humans, and may also carry trypanosomes and the protozoan Pneumocystis carinii.

Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses

This is a review of the research undertaken since 1971 on the behavior and physiological ecology of sloths. The animals exhibit numerous fascinating features. Sloth hair is extremely specialized for a wet tropical environment and contains symbiotic algae. Activity shows circadian and seasonal variation. Nutrients derived from the food, particularly in Bradypus, only barely match the requirements for energy expenditure. Sloths are hosts to a fascinating array of commensal and parasitic arthropods and are carriers of various arthropod-borne viruses. Sloths are known reservoirs of the flagellate protozoan which causes leishmaniasis in humans, and may also carry trypanosomes and the protozoan Pneumocystis carinii