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Tuber­cu­lo­sis diag­no­sis in rhi­noc­eros improved by using lung lavage test method

pub­lished 18 Decem­ber 2018 | mod­i­fied 18 Decem­ber 2018

Dis­eases and tuber­cu­lo­sis in par­tic­u­lar can pose con­sid­er­able chal­lenges for wildlife. In order to avoid epi­demics within pop­u­la­tions or to treat indi­vid­ual ani­mals belong­ing to highly endan­gered species, fast and reli­able tests are para­mount. Unfor­tu­nately, present tuber­cu­lo­sis test­ing in rhi­nos relies on skin tests devel­oped and designed in the 1960s for cat­tle that bears a high risk of false diag­no­sis in rhi­nos. To improve diag­nos­tic stan­dards an inter­na­tional team of sci­en­tists lead by insti­tutes in Berlin and Jena, Ger­many, per­formed repeated lung lavage as a new approach for tuber­cu­lo­sis diag­no­sis in rhi­noc­eros. Sub­se­quent genetic tests reli­ably iden­ti­fied mycobac­te­ria in the ani­mals’ res­pi­ra­tory flu­ids – with min­i­mal stress and risk for the rhinos.

white rhino lung lavageRhino lung lavage pro­ce­dure. Sedated white rhi­noc­eros with endo­scope inserted into the right nos­tril.
Source: Dif­fer­en­tial detec­tion of tuber­cu­lous and non-​tuberculous mycobac­te­ria by qPCR in lavage flu­ids of tuberculosis-​suspicious white rhi­noc­eros by Robert Her­mes et al.,2018, PLOS ONE.

Con­ven­tional immuno­log­i­cal tests for tuber­cu­lo­sis in rhi­noc­eros are sub­stan­tially inse­cure and bear high risk of false neg­a­tive or false pos­i­tive diag­no­sis with some­times fatal con­se­quences for the ani­mal. At present only exam­i­na­tions car­ried out on deceased ani­mals allow a reli­able tuber­cu­lo­sis diag­no­sis. This sit­u­a­tion has been the start­ing point for the team of sci­en­tists at the Leib­niz Insti­tute for Zoo and Wildlife Research (Leibniz-​IZW) and the Friedrich-​Loeffler-​Institut (Fed­eral Research Agency for Ani­mal Health, FLI) to genet­i­cally analyse lung lavage flu­ids for mycobac­te­ria as a new approach for tuber­cu­lo­sis diag­no­sis in these mas­sive pachy­derms. This required a short stand­ing seda­tion, endo­scopic explo­ration of the rhi­noc­eros lung and col­lec­tion of res­pi­ra­tory flu­ids. The col­lected flu­ids were tested for the pres­ence of genetic mate­r­ial from mycobac­te­ria in gen­eral and tuber­cu­lo­sis pathogens in par­tic­u­lar. In par­al­lel, the sam­ples were cul­tured under spe­cial con­di­tions to fos­ter the growth of viable mycobacteria.

There are two groups of mycobac­te­ria, dif­fer­ing in their haz­ardous nature”, explains Robert Her­mes from Leibniz-​IZW. “On the one hand there are a few mycobac­te­ria belong­ing to the Mycobac­terium tuber­cu­lo­sis com­plex which can cause tuber­cu­lo­sis. On the other hand there are numer­ous mostly harm­less mycobac­te­ria not asso­ci­ated with any dis­ease.” The lat­ter ones are very com­mon in the envi­ron­ment and rhi­noc­er­oses as strict graz­ers are immensely exposed to them. For that rea­son tests for tuber­cu­lo­sis pathogens need to be very fail-​safe in dif­fer­en­ti­at­ing between these two groups of mycobac­te­ria. Con­ven­tional immuno­log­i­cal skin and blood tests for rhi­nos often indi­cate immuno­log­i­cal reac­tions which turn out to be reac­tions to harm­less mycobac­te­ria after euthana­sia of the ‘tuberculosis-​suspicious’ animals.

In this study, pub­lished on 28 Novem­ber in the jour­nal PLOS ONE, repeated lung lavage was per­formed on 7 rhi­nos from Euro­pean Zoos with a total of 21 fluid col­lec­tions with sub­se­quent lab­o­ra­tory analy­sis. This approach proved the supe­ri­or­ity of the new endo­scopic approach. It was found that lung flu­ids of all ani­mals revealed the pres­ence of DNA from only harm­less mycobac­te­ria. The dan­ger of false diag­no­sis of the tuber­cu­lo­sis (false pos­i­tive result) could now be reduced in the future using lung lavage. “Pre­clud­ing an infec­tion with tuber­cu­lo­sis pathogens, how­ever, can­not be achieved by a sin­gle exam­i­na­tion”, adds Ste­fanie Barth from the National Ref­er­ence Lab­o­ra­tory for Bovine Tuber­cu­lo­sis at the FLI. In order to rule out false neg­a­tive results (where an ani­mal is infected while the test does not indi­cate that) the sci­en­tists rec­om­mend repeated tests on tuberculosis-​suspicious rhi­noc­eros. A guar­an­tee does not come with this, but the approach deliv­ers results that are far closer to a reli­able diag­no­sis than con­ven­tional tests, for exam­ple skin tests, on liv­ing rhinos.

white rhino respiratory tract endoscopyA-​D endo­scopic views of the res­pi­ra­tory tract in the white rhi­noc­eros. A: View of the epiglot­tis and rima vocalis below the open­ing to the dor­sal air sac. B: View of the epiglot­tis and rima vocalis. Swollen lym­phatic tis­sue sur­rounds the open­ing of the dor­sal air sac. C: View of the tra­chea, carina tra­cheae and two main bronchi sep­a­rat­ing left from right lung. D: View onto the carina tra­cheae and bifur­ca­tio into smaller bronchi or each lung.
Source: Dif­fer­en­tial detec­tion of tuber­cu­lous and non-​tuberculous mycobac­te­ria by qPCR in lavage flu­ids of tuberculosis-​suspicious white rhi­noc­eros by Robert Her­mes et al.,2018, PLOS ONE.

Infec­tions with tuber­cu­lo­sis pose a threat to humans and live­stock. In regions where wild and farmed ani­mals get into con­tact the risk of bidi­rec­tional spill-​over is a real and press­ing prob­lem. Sci­en­tists assume that the African buf­falo pop­u­la­tion in South Africa became infected by bovine tuber­cu­lo­sis through its inter­ac­tion with infected domes­tic cat­tle. The buf­fa­los are now act­ing as main­te­nance hosts and spread the dis­ease to car­ni­vores feed­ing on them as well as to other species with which they come into con­tact. To date a large num­ber of wildlife species – among them crit­i­cally endan­gered species — were tested pos­i­tive for bovine tuber­cu­lo­sis includ­ing lion, greater kudu, chee­tah, spot­ted hyena, leop­ard, and rhi­noc­eros. The dis­ease is a zoono­sis, which means it can be nat­u­rally trans­mit­ted between ani­mals and humans. There­fore, in this case, research into wildlife dis­eases is also tar­get­ing the ben­e­fit of mankind.

And once again the mis­sion of zoo­log­i­cal gar­dens to con­tribute to research, includ­ing research on cap­tive pop­u­la­tion of ani­mal species in zoos, has proven its value.


(Source: Leib­niz Forschungver­bund Berlin e.V. press release, 12.12.2018)

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