Serological evidence of herpesvirus infection in captive Asian elephants (Elephas maximus)

THE IMPACT OF ELEPHANT ENDOTHELIOTROPIC HERPESVIRUS ON THE CAPTIVE ASIAN ELEPHANT (ELEPHAS MAXIMUS) POPULATION OF THE UNITED KINGDOM AND IRELAND (1995-2013)

Elephant endotheliotropic herpesvirus (EEHV) is one of the most devastating infections and causes of mortality in captive Asian elephant ( Elephas maximus ) populations. Eight confirmed fatal EEHV cases have occurred since 1995 within the captive Asian elephant population of the United Kingdom and Ireland. This report aims to review the impact of EEHV on the captive Asian elephant population in the United Kingdom and Ireland, document and compare fatal cases, and recommend a framework of monitoring within the United Kingdom and Ireland to increase the success of treatment of EEHV hemorrhagic disease (EEHV HD) in the future. Six zoologic institutions (which include zoos, safari parks, and wildlife parks) that currently house or have previously housed a captive Asian elephant group were included in this report. Medical records and postmortem results were collected from four of these institutions for each confirmed fatal case. EEHV HD was found to be responsible for 29.6% of fatalities in Asian elephants born in captivity in the United Kingdom and Ireland between 1995 and 2013. Following a review of all the cases, it is shown that although clinical signs may be associated with specific EEHV species, the swiftness of disease progression means that most body tissues are impacted 1-6 days following the presentation of visible clinical signs and treatment is less likely to succeed. Therefore, EEHV monitoring should consist of conducting regular polymerase chain reaction analysis of whole blood samples from at-risk, young Asian elephants aged 1-8 yr in order for subclinical viremia to be identified early and treatment to be started before the appearance of visible clinical signs.

A novel antigen capture ELISA for the specific detection of IgG antibodies to elephant endotheliotropic herpes virus

BACKGROUND

Elephants are classified as critically endangered animals by the International Union for Conservation of Species (IUCN). Elephant endotheliotropic herpesvirus (EEHV) poses a large threat to breeding programs of captive Asian elephants by causing fatal haemorrhagic disease. EEHV infection is detected by PCR in samples from both clinically ill and asymptomatic elephants with an active infection, whereas latent carriers can be distinguished exclusively via serological assays. To date, identification of latent carriers has been challenging, since there are no serological assays capable of detecting seropositive elephants.

RESULTS

Here we describe a novel ELISA that specifically detects EEHV antibodies circulating in Asian elephant plasma/serum. Approximately 80 % of PCR positive elephants display EEHV-specific antibodies. Monitoring three Asian elephant herds from European zoos revealed that the serostatus of elephants within a herd varied from non-detectable to high titers. The antibody titers showed typical herpes-like rise-and-fall patterns in time which occur in all seropositive animals in the herd more or less simultaneously.

CONCLUSIONS

This study shows that the developed ELISA is suitable to detect antibodies specific to EEHV. It allows study of EEHV seroprevalence in Asian elephants. Results confirm that EEHV prevalence among Asian elephants (whether captive-born or wild-caught) is high.

The occurrence of elephant endotheliotropic herpesvirus in captive Asian elephants (Elephas maximus): first case of EEHV4 in Asia

Elephant endotheliotropic herpesvirus (EEHV) is a type of herpesvirus that causes acute hemorrhagic disease in Asian elephants (Elephas maximus) and is often fatal, especially in calves. This study describes the postmortem evaluation of two captive-born Asian elephants (2 and 3 yr of age, respectively) diagnosed with EEHV in Thailand. Both elephants presented only mild depression, lethargy, and anorexia before death within 24 hr of symptom onset. Necropsies were performed, and tissue samples were tested for EEHV viral presence using polymerase chain reaction. Molecular and phylogenetic evidence illustrated two types of EEHV, which were closely related to EEHV1A in Case 1 and EEHV4 in Case 2. Pathologic findings differed between the cases. More specific organ tropism was found in Case 1, where mainly the cardiovascular system was affected. In contrast, in Case 2, hemorrhages were noted in most organs, including in the gastrointestinal, respiratory, and cardiovascular systems. This report is the first to document EEHV4 in Asia and the second case of this strain to be identified in an elephant worldwide.

A preliminary analysis of the immunoglobulin genes in the African elephant (Loxodonta africana)

The genomic organization of the IgH (Immunoglobulin heavy chain), Igκ (Immunoglobulin kappa chain), and Igλ (Immunoglobulin lambda chain) loci in the African elephant (Loxodonta africana) was annotated using available genome data. The elephant IgH locus on scaffold 57 spans over 2,974 kb, and consists of at least 112 V(H) gene segments, 87 D(H) gene segments (the largest number in mammals examined so far), six J(H) gene segments, a single μ, a δ remnant, and eight γ genes (α and ε genes are missing, most likely due to sequence gaps). The Igκ locus, found on three scaffolds (202, 50 and 86), contains a total of 153 V(κ) gene segments, three J(κ) segments, and a single C(κ) gene. Two different transcriptional orientations were determined for these V(κ) gene segments. In contrast, the Igλ locus on scaffold 68 includes 15 V(λ) gene segments, all with the same transcriptional polarity as the downstream J(λ)-C(λ) cluster. These data suggest that the elephant immunoglobulin gene repertoire is highly diverse and complex. Our results provide insights into the immunoglobulin genes in a placental mammal that is evolutionarily distant from humans, mice, and domestic animals.

Detection of pathogenic elephant endotheliotropic herpesvirus in routine trunk washes from healthy adult Asian elephants (Elephas maximus) by use of a real-time quantitative polymerase chain reaction assay

OBJECTIVE

To investigate the pathogenesis and transmission of elephant endotheliotropic herpesvirus (EEHV1) by analyzing various elephant fluid samples with a novel EEHV1-specific real-time PCR assay.

ANIMALS

5 apparently healthy captive Asian elephants (Elephas maximus) from the same herd.

PROCEDURES

A real-time PCR assay was developed that specifically detects EEHV1. The assay was used to evaluate paired whole blood and trunk-wash samples obtained from the 5 elephants during a 15-week period. Deoxyribonucleic acid sequencing and viral gene subtyping analysis were performed on trunk-wash DNA preparations that had positive results for EEHV1. Viral gene subtypes were compared with those associated with past fatal cases of herpesvirus-associated disease within the herd.

RESULTS

The PCR assay detected viral DNA to a level of 1,200 copies/mL of whole blood. It was used to detect EEHV1 in trunk secretions of 3 of the 5 elephants surveyed during the 15-week period. Viral gene subtyping analysis identified 2 distinct elephant herpesviruses, 1 of which was identical to the virus associated with a previous fatal case of herpesvirus-associated disease within the herd.

CONCLUSIONS AND CLINICAL RELEVANCE

EEHV1 was shed in the trunk secretions of healthy Asian elephants. Trunk secretions may provide a mode of transmission for this virus. Results of this study may be useful for the diagnosis, treatment, and management of EEHV1-associated disease and the overall management of captive elephant populations.

Novel endotheliotropic herpesviruses fatal for Asian and African elephants

A highly fatal hemorrhagic disease has been identified in 10 young Asian and African elephants at North American zoos. In the affected animals there was ultrastructural evidence for herpesvirus-like particles in endothelial cells of the heart, liver, and tongue. Consensus primer polymerase chain reaction combined with sequencing yielded molecular evidence that confirmed the presence of two novel but related herpesviruses associated with the disease, one in Asian elephants and another in African elephants. Otherwise healthy African elephants with external herpetic lesions yielded herpesvirus sequences identical to that found in Asian elephants with endothelial disease. This finding suggests that the Asian elephant deaths were caused by cross-species infection with a herpesvirus that is naturally latent in, but normally not lethal to, African elephants. A reciprocal relationship may exist for the African elephant disease.

In situ inactivation of animal viruses and a coliphage in nonaerated liquid and semiliquid animal wastes

The persistence of five animal viruses, representing picorna-, rota-, parvo-, adeno-, and herpesviruses, and the coliphage f2 was determined in the field by exposing the viruses to different animal wastes and by adopting an established filter sandwich technique. This technique allows us to copy the natural state of viruses in the environment, where adsorption onto or incorporation into suspended solids may prolong virus survival. Using filter sandwiches either equipped with porous (15 nm in diameter) or poreless polycarbonate (PC) membranes, it was possible to differentiate between overall virus inactivation and the effect of virucidal agents that act through poreless PC membranes. Depending on ambient temperature, pH, and type of animal waste, values for time, in days, required for a 90% reduction of virus titer varied widely, ranging from less than 1 week for herpesvirus to more than 6 months for rotavirus. Virus inactivation progressed substantially faster in liquid cattle manure, a mixture of urine and water (pH > 8.0), than in semiliquid wastes that consisted of mixtures of feces, urine, water, and bedding materials (pH < 8.0). Hitherto unidentified virucidal agents that permeate poreless PC membranes contributed substantially to the overall inactivation. On the other hand, substances that protect rotavirus and possibly other viruses from inactivation may be present in animal wastes. Together, the study showed that viruses contained in manure may persist for prolonged periods of time if stored under nonaerated conditions. At times of land application, this may lead to environmental contamination with pathogens.

The malignant catarrhal fever complex

Malignant catarrhal fever (MCF) is defined as a clinicopathological syndrome caused by related herpesviruses and acquired from persistently infected wildebeest and sheep. There is convincing epidemiologic and virologic evidence that Alcelaphine herpesvirus 1 (AHV1) causes the wildebeest-derived disease (WD-MCF). Present knowledge suggests that a herpesvirus related to AHV1 may be associated with some cases of the non-wildebeest-associated disease (NWA-MCF). However, this virus possibly represents a passenger virus not related with the ultimate cause of the disease. Moreover, evidence for the role played by sheep as the reservoir for the agent of NWA-MCF is not convincing and awaits confirmation.