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201610Jan17:26

Ore­gon Zoo staff con­tracted tuber­cu­lo­sis from the Zoo’s ele­phants in 2013

Infor­ma­tion
pub­lished 10 Jan­u­ary 2016 | mod­i­fied 10 Jan­u­ary 2016
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Oregon Zoo elephant PackySeven employ­ees of the Ore­gon Zoo in Port­land have con­tracted a latent form of tuber­cu­lo­sis in 2013 from three of the Zoo’s ele­phants. This infor­ma­tion was pub­lished by the Cen­ters for Dis­ease Con­trol and Pre­ven­tion (CDC) in Atlanta, USA, on 8 January.

Appar­ently the CDC report was issued due to the rul­ing of a judge in a law­suit filed by the animal-​rights group Peo­ple for the Eth­i­cal Treat­ment of Ani­mals (PETA) against the CDC’s par­ent orga­ni­za­tion the U.S. Depart­ment of Health and Human Ser­vices. Infor­ma­tion on the tuber­cu­lo­sis inves­ti­ga­tion regard­ing the Ore­gon Zoo ele­phants had to be revealed. PETA wanted release of the infor­ma­tion because of the risk involved when ele­phants would spread the poten­tially deadly dis­ease to other ele­phants or to humans.

Ele­phant tuber­cu­lo­sis
Tuber­cu­lo­sis (TB) is a res­pi­ra­tory dis­ease that is spread through the air when a per­son — or in this case ele­phant — coughs, sneezes or oth­er­wise spreads the pathogen, a bac­te­ria. TB is a well-​known dis­ease and cause of death in ele­phants. The pathogen caus­ing TB, Mycobac­terium tuber­cu­lo­sis, is even impli­cated in the extinc­tion of the Amer­i­can mastodon. The first zoo ele­phant death which report­edly was infected by TB was an Asian ele­phant at Lon­don Zoo in 1875. But African ele­phants can suf­fer from TB too, as it was first reported in 1962. Both the human form (Mycobac­terium tuber­cu­lo­sis) and the bovine form (Mycobac­terium bovis) can cause infec­tion and dis­ease in ele­phants. The avian form (Mycobac­terium avium) is found in ele­phants but doesn’t cause dis­ease.

In 1983 a cir­cus ele­phant in North Amer­ica was diag­nosed with TB. Though nobody recog­nised it at the time, this report pre­dicted a prob­lem for cap­tive ele­phants in North Amer­ica and Europe that only would show more than a decade later. In 1996 TB re-​emerged in ele­phants in the U.S. with the death of again two cir­cus ele­phants. But more sig­nif­i­cant was the diag­no­sis of 5 new ele­phants with TB at 4 other facil­i­ties. And per­haps even more impor­tant, TB in ele­phants proved to be a zoono­sis in 1997. Zoonotic trans­mis­sion of TB from ele­phants to humans work­ing in close prox­im­ity was described in the late 1990s. Obvi­ously TB in cap­tive ele­phant herds was an issue to be addressed seri­ously. So, the first guide­lines for the con­trol of TB in zoo ele­phants were pro­duced in 1998.

In North Amer­ica, approx­i­mately 5% of the cap­tive Asian ele­phants are infected with M. tuber­cu­lo­sis, based on pos­i­tive cul­tures of trunk wash­ing sam­ples or necropsy results. How­ever, not only ele­phants in the USA are sus­cep­ti­ble to TB. Until 2008 seven ele­phant TB cases have been reported in Europe, while 59 of 387 cap­tive ele­phants had TB in four states of south­ern India.

TB in cap­tive ele­phants is a re-​emerging zoonotic dis­ease. A zoono­sis is an infec­tion ‘shared in nature by man and ani­mals’ accord­ing the def­i­n­i­tion of the World Health Organ­i­sa­tion. Basi­cally a dis­ease is con­sid­ered a zoono­sis when the infec­tion is trans­ferred from ani­mal to human, and as a reverse zoono­sis when the infec­tion is trans­ferred from human to animal.

The 2013 Ore­gon Zoo case
In May 2013, a 20-​year-​old Asian ele­phant bull at the Ore­gon Zoo was diag­nosed with TB dur­ing a rou­tine annual cul­ture of a sam­ple from a trunk wash­ing. In addi­tion, two other bulls were detected with the same disease.

CDC Atlanta together with Ore­gon Zoo iden­ti­fied three dif­fer­ent groups of peo­ple who had con­tact with these three ele­phants. Within the group of close con­tacts, 19 zoo employ­ees, 6 per­sons testes pos­i­tive for TB but were non-​infectious. Ret­ro­spec­tively (back to 2010) another 22 close con­tacts were iden­ti­fied which resulted in another one TB pos­i­tive non-​infectious con­tact. A total of 7 per­sons were found to have a so-​called latent TB infec­tion.
Within the group of 39 casual con­tacts and a group of 20 con­tacts who had attended spe­cial events at which the ele­phants sprayed paint with their trunk onto can­vases behind atten­dees, no per­sons were tested pos­i­tive. But some time later another casual con­tact was iden­ti­fied. This turned out to be some­one who had devel­oped a pleural TB that prob­a­bly wasn’t infec­tious. This patient had worked at the zoo inter­mit­tently dur­ing 2012, but had only lim­ited con­tact with the elephants.

So, of all employ­ees who have been found infected with this dor­mant type of TB, one showed symp­toms (pleural TB) but none were contagious.

Rama, a 31-​year-​old Asian ele­phant (and son of Packy) known for his sweet dis­po­si­tion and Jack­son Pollock-​like paint­ing tech­nique, was humanely euth­a­nized at the Ore­gon Zoo on 30 March 2015 after animal-​care staff deter­mined they could no longer help pain and mobil­ity issues result­ing from a 25-​year-​old leg injury:


(Source: Ore­gon Zoo YouTube channel)

Although sub­ject to con­tro­versy among ele­phant vet­eri­nar­i­ans the CDC report sug­gests to improve screen­ing for detect­ing TB in cap­tive ele­phant herds because trunk-​wash sam­ple cul­tures, the stan­dard for diag­nos­ing active TB in ele­phants, are insen­si­tive and lim­ited by poor accu­racy. There­fore, some cases of TB might be missed. In a 2009 arti­cle on highly accu­rate anti­body test­ing for TB detec­tion in ele­phants the authors say anti­body test­ing will likely allow ear­lier and more effi­cient treat­ment, thus lim­it­ing trans­mis­sion of infec­tion to other sus­cep­ti­ble ani­mals and to humans. CDC agrees that fur­ther devel­op­ment of improved TB screen­ing meth­ods for ele­phants is needed to pre­vent expo­sure to humans with close and pro­longed contact.

The cause of the out­break is still unclear, but it could be that one of the ele­phants con­tracted TB from a human being. After all TB is a zoono­sis whereby the pathogen can be trans­ferred from human to ani­mal as well.

Treat­ment of ele­phants
Ele­phants with TB typ­i­cally are not euth­a­nized, but iso­lated and treated to pre­vent infec­tion of other ani­mals and humans. Many ele­phants have appar­ently been treated suc­cess­fully to date, but unfor­tu­nately the suc­cess rate is not 100%. The cost of treat­ment is around 50,000 per ani­mal. More­over there are addi­tional costs for the lab work, the iso­la­tion and the employee’s time. It is a labour inten­sive treat­ment procedure.

The Ore­gon Zoo in Port­land has announced that it will per­form reg­u­lar assess­ments on the ele­phants and the work­ers through at least June 2016.

Watch Packy, August 2014 — at 52 the old­est male Asian ele­phant in North Amer­ica — starts his day by play­ing with a water can­non and toss­ing around a 500-​pound log in the ele­phant swim­ming hole at the Ore­gon Zoo:


(Source: Ore­gon Zoo YouTube channel)


(Source: Reuters news release, 09.01.2016; CDC Mor­bid­ity and Mor­tal­ity Weekly Report, 08.01.2016; Tuber­cu­lo­sis in ele­phants: a reverse zoono­sis, by Arnon Shimshony in Healio, Decem­ber 2008; web­site ele­phant­care; A Brief His­tory of TB in Ele­phants by Susan K. Mikota; Review of Tuber­cu­lo­sis in Cap­tive Ele­phants and Impli­ca­tions for Wild Pop­u­la­tions by Susan K. Mikota in Gajah, 2008; Highly Accu­rate Anti­body Assays for Early and Rapid Detec­tion of Tuber­cu­lo­sis in African and Asian Ele­phants by Green­wald et al. in Clin­i­cal and Vac­cine Immunol­ogy, 04.03.2009; Tuber­cu­lo­sis treat­ment pro­to­cols and com­pli­ca­tions for ele­phants by Genevieve Dumon­ceaux and Susan Mikota)


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