Zoonoses

Zoonotic diseases in elephants.

Zoonotic diseases are defined as infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that can jump from a non-human (usually a vertebrate) to a human and vice versa. Some of these pathogens can be considered as opportunistic, others as primary infections.

Relevant primary pathogens in elephants are:

Bacterial diseases

Mycobacterium tuberculosis complex (MTBC). The prevalence of MTBC in captive elephants in European zoos is relatively high. A study of the post-mortem reports between 1985 and 2024 showed that 10/295 Asian elephants and 12/195 African elephants had died of MTBC (Data from EAZA elephant TAG, WS).
From 1997 through 2011, the median point of prevalence within the Asian elephant population in USA-zoos was 5.1%, with a range from 0.3% to 6.7%. In contrast, the annual point prevalence during the same time period within the African elephant population was 0. Although exact data about the prevalence of MTBC in range countries are not known, there are many reports of MTBC in captive and to (a lesser degree) wild Asian elephants. Data on MTBC in African elephants in range countries are limited. Click here to read more about tuberculosis in elephants.
Non-tuberculous mycobacteriosis: Mycobacterium elephantis; only found in humans, never in elephants. However, the strain is genetically related to Mycobacterium confluentis and M. smegmatis cultured form lung lesions in an elephant (Lacasse, 2007).
Bacillus anthrax: Click here to read more about anthrax in elephants.
Pasteurella multocida: Click here to read more about Pasteurellosis in elephants.
Salmonella spp.: Click here to read more about salmonellosis in elephants.
Leptospira interrogans found in urine of captive elephants in Asia. This is a potential risk for humans in close contact with these elephants (Athapattu 2019). Click here to read more about leptospirosis in elephants.

Viral diseases:

Cowpox virus (Orthopoxvirus bovis). Asian elephants are very sensitive to a pox virus infection, African elephants to a lesser degree. The fluid that fill the pox vesicles are full of virus. Once the fluid is exposed, humans can become infected. Click here to read more about pox virus infections in elephants.
Foot and Mouth disease virus (FMD-virus): Asian elephants are very sensitive to FMD. There is only one report of FMD in an African elephant that was experimentally infected. Click here to read more about FMD in elephants.
Rabies: transmission of rabies virus from elephants to humans have never been reported, but saliva of diseased rabid elephant is a potential risk for humans. Click here to read more about rabies in elephants.

Opportunistic pathogens:

Opportunistic pathogens can be found in the environment, but when concentrated in a pathological condition in an animal (abscess, feces, urine, exudate), they can cause disease in humans:

Escherichia coli
Pseudomonas
Bacteroides spp.
Staphylococcus aureus
Streptococcus spp.
Klebsiella spp.
Mycobacterium avium
Fungi: there are no reports on fungus infections in humans acquired through contact with elephants.

Serological responses detected in elephants without evidence of causing disease:

Elephants may be (temporary) silent carriers of several potentially pathogenic microbes. The historical contact is expressed by the presence of antibodies in the blood of the elephant. Examples of these conditions are:

African horse sickness virus: the presence of antibodies in African elephants has been described (Barnard, 1995). Humans are usually not affected. However, severe disease has been reported in lab workers who were producing a AHSV-vaccine (van der Meyden, 1991; Reid,1991).
Influenza type A: 1 serologically positive elephant reported (Schröder 1992).
Eastern equine encephalitis: 1 serologically positive elephant reported (Christy, 2009)
Bluetongue: antibodies were detected in 7 out of 109 serum samples of captive Asian elephants in India (Bhat, 1998).
Canine distemper: antibodies were detected in 25 out of 144 serum samples of captive Asian elephants in Thailand (Ono, 2006).
Yersinia pestis (plague); In one study in wild African elephants 0.3% of the cohort animals were found seropositive for antibodies against Yersinia pestis (Gordon, 1979). No transmission of plague from elephants to humans has been reported.
Toxoplasma gondii: 35% of captive elephants in a study in Thailand was serologically positive (Udonsom 2022). As the elephant is not an end-host for toxoplasmosis, transmission of toxoplasmosis from elephants to humans is unlikely to occur.
Cryptosporidium spp.: found in African elephants at a European zoo (Gracena, 2002). No transmission to humans has been reported.

References

Athapattu TPJ, Fernando BR, Koizumi N, Gamage CD. Detection of pathogenic leptospires in the urine of domesticated elephants in Sri Lanka. Acta Trop. 2019 Jul;195:78-82. doi: 10.1016/j.actatropica.2019.04.029. Epub 2019 Apr 29. PMID: 31047864.
Barnard BJH, Bengi RG, Keet DF, Dekker EH, Verwoerd DW. 1995. Epidemiology of African horsesickness: antibodies in free-living elephants (Loxodonta africana) and their response to experimental infection. Onderstepoort journal of Vet. Res. 62, 1995.
Bhat N, Manickam R, Arunp W.1998. Detection of bluetongue antibody and antigen in Indian elephants, spotted deer and blackbucks. Indian Journal of Animal Sciences 68 (2) : 135, February 1998
Christy L. Rettenmund CL, Terrell SP, Miller M. 2009 Eastern Equine Encephalitis Virus (EEEV) Titers in African Elephants (Loxodonta africana) At Disney’s Animal Kingdom. American association of Zoo Veterinarians Conference 2009
Feldman M, Isaza R, Prins C, Hernandez J. 2013. Point prevalence and incidence of Mycobacterium tuberculosis complex in captive elephants in the United States of America, Veterinary Quarterly, 33:1, 25-29.
Gordon DH, Isaacson M, Taylor P. 1979. Plague Antibody in Large African Mammals. Infection and Immunity, Nov. 1979, p. 767-769
Gracenea M, Gómez M., Torres J, Carné E, Fernández-Morán J. 2002. Transmission dynamics of Cryptosporidium in primates and herbivores at the Barcelona zoo: a long-term study. Veterinary Parasitology, 104(1), 19–26. doi:10.1016/s0304-4017(01)00611-2.
Lacasse C, Terio K, Kinsel MJ, Farina LL, Travis DA, Greenwald R, Lyashchenko MDKP, Miller M, Gamble KC. 2007. Two cases of atypical mycobacteriosis caused by Mycobacterium szulgai associated with mortality in captive african elephants (Loxodonta africana). Journal of Zoo and Wildlife Medicine 38(1): 101–107, 2007.
Oni O, Wajjwalku W, Boodde O, Chumsing W. 2013. Canine distemper virus antibodies in the Asian elephant (Elephas maximus). The Veterinary Record, September 23, 2006.
Reid, R, van der Meyden, CH, Erasmus, BJ, Meyer, H and Hamilton, AMP. 1991. Encephalitis and chorioretinitis associ[1]ated with neurotropic African horsesickness virus infection in laboratory workers. Part II. Ophthalmological findings. S Afr Med J 81:454–458.
Schröder, H.D., Fischer, M. and Ippen, R. 1992. Contribution to the occurrence of infection of zoo mammals with influenzavirus type A. Erkrankungen der Zootiere. Verhandlungsbericht des 34. Internationalen Symposiums uber die Erkrankungen der Zoo- und Wildtiere, Santander-Spain, pp. 119–125.
Udonsom R, Nishikawa Y, Fereig RM, Topisit T, Kulkaweewut N, Chanamrung S, Jirapattharasate C.2022. Exposure to Toxoplasma gondii in Asian Elephants (Elephas maximus indicus) in Thailand. Pathogens 2022, 11, 2.
van der Meyden, CH, Erasmus, BJ, Swanepoel, R. and Prozesky, OW. 1991. Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part I. Clinical and neurological observa[1]tions. S Afr Med J 81:451–454.
Zachariah A, Pandiyan J, Madhavilatha G, Mundayoor S, Chandramohan B, Sajesh P, et al. Mycobacterium tuberculosis in Wild Asian Elephants, Southern India. Emerg Infect Dis. 2017;23(3):504-506. https://doi.org/10.3201/eid2303.161741

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