Vaccination of Llamas, Llama glama, with an Experimental Killed Encephalomyocarditis Virus Vaccine

Abstract

Encephalomyocarditis virus (EMCV) is a pandemic virus that has caused mortality in numerous captive wildlife species worldwide. An experimental killed vaccine was created from two EMCV isolates associated with zoo animal mortality in the southern United States. The vaccine was tested for safety and efficacy in eleven llamas (Llama glama). All animals received an initial vaccination and a second booster vaccination 4 wk later. Serum antibody responses were monitored at initial vaccination and at 4 wks, 8 wk, 6 mo, and 12 mo postvaccination. Eight of the 11 llamas vaccinated experienced at least a 4-fold increase in serum antibody titers to EMCV. Antibody titers of those eight animals remained elevated above prevaccination levels when measured at 12 mo. The experimental killed EMCV vaccine tested may be a useful tool to prevent EMCV infection in llamas when given in 2 doses 4 wk apart, and then revaccinated or with antibody levels monitored annually thereafter.

A retrospective analysis of mortality in captive pygmy hippopotamus (Choeropsis liberiensis) from 1912 to 2014

“…The situation with EMCV leads us to strongly recommend that all cases of acute death in pygmy hippos be submitted to a reference laboratory for serology testing and virus isolation whenever post‐mortem findings indicate a cardiovascular etiology. Commercial vaccines for EMCV are not currently available, but experimental vaccines (inactivated and modified live) have been used in clinical trials and outbreak situations [Gaskin et al, ; Wells et al, ; Osorio et al, ; Hunter et al, ; McLelland et al, ; Kilburn et al, ]. Although seroconversion and efficacy are variable, side‐effects were not reported after experimental vaccination in numerous other ungulate species including llamas ( Llama glama ), guanacos ( Lama glama guanicoe ), Bactrian camels ( Camelus bactrianus ), dromedary camels ( Camelus dromedarius ), Barbary sheep ( Ammotragus lervia ), gerenuk ( Litocranius walleri ), blackbuck ( Antilope cervicapra ), black duikers ( Cephalophus niger ), lowland tapirs ( Tapirus terrestris ), Baird's tapirs ( Tapirus bairdii ), Malayan tapirs ( Tapirus indicus ), babirusas ( Babyrousa babyrussa ), and collared peccaries ( Tayassu tajacu ) [McLelland et al, ; Backues, ; Kilburn et al, ].…”

Genome Sequencing of Historical Encephalomyocarditis Viruses from South Africa Links the Historical 1993/4 Savanna Elephant (Loxodonta africana) Outbreak to Cryptic Mastomys Rodents

“…It is therefore important to control the spread of EMCV. This can be achieved through available emergency vaccination in captive and wild populations [ 69 , 70 , 71 ] and effective rodent–pest control programs that limit transmission of EMCV by rodents via the faecal–oral route by removing them from captive environments and pig operations [ 13 , 72 ].…”

Encephalomyocarditis virus in a capybara (Hydrochoerus hydrochaeris)

“…[48][49][50] Variation in immune response after vaccination is common, and factors such as antigen concentration, viral strain, adjuvant and host immunocompetence may affect immunity. 51 Naturally acquired antibody titres do not appear to persist despite endemic infection, and high titres are not necessarily protective. 9 Viral dose and environment factors including stress may also have resulted in increased susceptibility.…”

“…Administration of antibodies and a DNA vaccine have also been reported to provide effective protection in mice, and a genetically engineered Mengo virus vaccine has been reported to provide immunity in baboons, macaques and domestic pigs 48–50 . Variation in immune response after vaccination is common, and factors such as antigen concentration, viral strain, adjuvant and host immunocompetence may affect immunity 51 . Naturally acquired antibody titres do not appear to persist despite endemic infection, and high titres are not necessarily protective 9 .…”