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Wednesday, July 29, 2009
Species Barrier May Protect Macaques from Chronic Wasting Disease
Data from an ongoing multi-year study suggest that people who consume deer and elk with chronic wasting disease (CWD) may be protected from infection by an inability of the CWD infectious agent to spread to people. The results to date show that 14 cynomolgus macaques exposed orally or intracerebrally to CWD remain healthy and symptom free after more than six years of observation, though the direct relevance to people is not definitive and remains under study. Cynomolgus macaques often are used as research models of human disease because they are very close genetically to humans and are susceptible to several forms of human brain-damaging disease. Thus, it was decided to see whether exposure to CWD could induce disease in the macaques. The study appears online in the journal Emerging Infectious Diseases.
CWD is a type of brain-damaging disease known as a transmissible spongiform encephalopathy (TSE) or prion disease. CWD primarily affects deer, elk, and moose. Other TSE diseases include mad cow disease, or bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep, and sporadic Creutzfeldt-Jakob disease (CJD) in humans. Humans are not susceptible to sheep scrapie, but BSE appears to have infected about 200 people, primarily in Europe in the 1990s. Those findings provided the rationale for the present CWD-macaque study, which began in 2003.
"We plan to continue this study for at least several more years because, although the risk to macaques so far appears to be low, we know that these diseases can take more than 10 years to develop," says Bruce Chesebro, M.D., chief of the Laboratory of Persistent Viral Diseases at Rocky Mountain Laboratories (RML) in Hamilton, Mont. RML is part of the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH). The RML group is leading the study with collaborators from the Colorado Division of Wildlife; State University of New York Downstate Medical Center; New York State Institute for Basic Research in Developmental Disabilities; American Red Cross; and the University of Wyoming.
The findings by the RML group support published field studies done by others in regions of Colorado and Wyoming where CWD is endemic. Between 1979 and 2001, there were no significant increases in human TSE diseases despite the likelihood that hunters in those areas were exposed to CWD through contact with infected animal tissue and contaminated hunting tools such as knives and saws. Extensive laboratory data also supports a human species barrier against CWD.
Notably, the RML study also included identical testing in squirrel monkeys, which are genetically less similar to humans than macaques. Of 15 squirrel monkeys exposed orally to CWD, two displayed disease symptoms 69 months after infection. Of 13 squirrel monkeys exposed intracerebrally to CWD, 11 displayed symptoms between 33 and 53 months after infection. In symptomatic animals, the presence of the CWD agent was confirmed in brain, spleen and lymph nodes.
The results in squirrel monkeys were not surprising because a study elsewhere in two squirrel monkeys yielded similar results. The study by the RML group was different, however, in that it tested oral exposure to CWD and also studied eight CWD samples from different areas of the country. The results in squirrel monkeys confirmed that disease progression in that species appears consistent with disease progression in deer and elk, where severe weight loss is nearly always present.
"The fact that the squirrel monkeys, like the deer and elk, suffered severe weight loss suggests that chronic wasting disease might affect a common region of the brain in different species," notes Dr. Chesebro.
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"Kama ilivyoelezwa hapo juu, ""Mkingo wa spishi unaweza kulinda macaques kutoka kwa ugonjwa wa kupoteza muda mrefu"" - data kutoka kwa utafiti unaoendelea wa miaka mingi unaonyesha kwamba watu wanaokula nyati na elk na ugonjwa wa kupoteza muda mrefu (CWD) wanaweza kulindwa kutoka kwa maambukizi kwa kutokuwa na uwezo wa maambukizi ya CWD kuenea kwa watu." Matokeo ya hivi sasa yanaonyesha kwamba macaques 14 za cynomolgus zilizoathiriwa na CWD kwa mdomo au intracerebral bado zina afya na hawana dalili baada ya zaidi ya miaka sita ya uchunguzi, ingawa umuhimu wa moja kwa moja kwa watu haujathibitishwa na bado unachunguzwa. Mnyama anayeitwa Cynomolgus macaque hutumiwa kama mfano wa utafiti wa magonjwa ya binadamu kwa sababu wanafanana sana na binadamu na wanaweza kuambukizwa magonjwa kadhaa yanayoathiri ubongo wa binadamu. Kwa hiyo, iliamuliwa kuona ikiwa kuambukizwa kwa CWD kwaweza kusababisha ugonjwa katika nyani hao. Utafiti huo umechapishwa kwenye jarida la Emerging Infectious Diseases. Ugonjwa wa ubongo unaoweza kuambukizwa kwa njia ya spongiform encephalopathy (TSE) au ugonjwa wa prion. Ugonjwa huo huathiri hasa nyati, elk, na moose. Ugonjwa wa TSE ni pamoja na ugonjwa wa ng'ombe wazimu, au ugonjwa wa spongiform encephalopathy (BSE) katika ng'ombe, scrapie katika kondoo, na ugonjwa wa Creutzfeldt-Jakob (CJD) katika wanadamu. Watu hawawezi kuambukizwa na ugonjwa wa scrapie, lakini inaonekana kwamba BSE imeambukiza watu 200 hivi, hasa huko Ulaya katika miaka ya 1990. Matokeo hayo yalitokeza msingi wa utafiti huu wa CWD-macaque, ulioanza mwaka 2003. """Tuna mpango wa kuendelea na utafiti huu kwa angalau miaka kadhaa kwa sababu, ingawa hatari kwa macaques hadi sasa inaonekana kuwa ya chini, tunajua kwamba magonjwa haya yanaweza kuchukua zaidi ya miaka 10 kuendeleza,"" anasema Bruce Chesebro, MD, mkuu wa Maabara ya Magonjwa ya Virusi ya Kudumu katika Rocky Mountain Laboratories (RML) huko Hamilton, Mont." RML ni sehemu ya Taasisi ya Taifa ya Madhara na Magonjwa ya Kuambukiza (NIAID) ya Taasisi ya Taifa ya Afya (NIH). RML inaongoza utafiti na washirika kutoka Idara ya Wanyamapori ya Colorado, Chuo Kikuu cha Jimbo la New York, Kituo cha Matibabu cha Downstate, Taasisi ya Jimbo la New York ya Utafiti wa Msingi katika Ulemavu wa Maendeleo, Msalaba Mwekundu wa Amerika, na Chuo Kikuu cha Wyoming. Utafiti huo unaunga mkono utafiti uliofanywa na wataalamu wa afya katika maeneo ya Colorado na Wyoming ambapo ugonjwa huo ni wa kawaida. Kati ya mwaka 1979 na 2001, hakukuwa na ongezeko kubwa la magonjwa ya TSE kwa binadamu, licha ya uwezekano wa wawindaji katika maeneo hayo kuwa wamegunduliwa na CWD kupitia kuwasiliana na tishu za wanyama walioambukizwa na vifaa vya kuwinda vilivyochafuliwa kama vile visu na saws. Takwimu nyingi za maabara pia zinaunga mkono kizuizi cha spishi ya binadamu dhidi ya CWD. Utafiti huo pia ulijumuisha majaribio sawa katika nyani wa squirrel, ambao ni sawa na wanadamu kuliko macaques. Katika nyani 15 waliopatikana na ugonjwa wa CWD, mbili zilionyesha dalili za ugonjwa huo miezi 69 baada ya kuambukizwa. Katika nyani 13 waliopatikana na ugonjwa huo, 11 walikuwa na dalili za ugonjwa huo baada ya miezi 33 hadi 53. Katika wanyama wenye dalili, uwepo wa kiasili wa CWD ulithibitishwa katika ubongo, utando na kibofu cha lymph. Matokeo katika nyani wa squirrel hayakuwa ya kushangaza kwa sababu utafiti mahali pengine katika nyani wawili wa squirrel ulitoa matokeo kama hayo. Utafiti wa RML ulijumuisha uchunguzi wa maambukizi ya mdomo na sampuli nane za ugonjwa wa CWD kutoka maeneo tofauti nchini. Matokeo katika nyani squirrel alithibitisha kwamba magonjwa maendeleo katika spishi hiyo inaonekana sambamba na magonjwa maendeleo katika nyati na elk, ambapo uzito mkubwa hasara ni karibu daima sasa. "Ukweli kwamba nyani-swamp, kama vile nyati na elk, walipoteza uzito sana unaonyesha kwamba ugonjwa wa kupoteza uzito kwa muda mrefu waweza kuathiri eneo la kawaida la ubongo katika spishi tofauti-tofauti", asema Dakt. Chesebro. NIAID hufanya na inasaidia utafiti katika NIH, kote Marekani, na ulimwenguni kote, kujifunza sababu za magonjwa ya kuambukiza na ya kinga, na kuendeleza njia bora za kuzuia, kugundua na kutibu magonjwa haya. Taarifa za habari, karatasi za ukweli na vifaa vingine vinavyohusiana na NIAID vinapatikana kwenye tovuti ya NIAID kwenye http: www.niaid.nih.gov. Taasisi ya Kitaifa ya Afya (NIH) ni shirika la utafiti wa matibabu la Marekani, lina taasisi 27 na ni sehemu ya Idara ya Afya na Huduma za Binadamu. NIH ni shirika kuu la shirikisho linalofanya na kusaidia utafiti wa msingi, kliniki, na wa tafsiri ya matibabu, na linachunguza sababu, matibabu, na tiba kwa magonjwa ya kawaida na ya nadra. Kwa habari zaidi kuhusu NIH na programu zake, tembelea www.nih.gov. NIH...Kugeuza Ugunduzi kuwa Afya®