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A First - Mad Camel Disease Discovered In Algerian Camels |
| By Patricia Doyle PhD |
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Hello Jeff - Now we find prion disease in Dromedary aka Camels in Algeria. I am sure prion disease will be found in other parts of the world among camels. More studies will be needed and testing for Mad Camel disease will be needed at slaughter. 3.1% of Camels at one slaughterhouse were identified as having Mad Camel disease. That is the tip of the iceberg, I am sure. Patty Source: CDC, Emerging Infectious Diseases Journal 2018 vol 24 No 6, ahead of publication [summarised, edited] https://wwwnc.cdc.gov/eid/ article/24/6/17-2007_article Citation: Babelhadj B, Di Bari MA, Pirisinu L, Chiappini B, Gaouar SBS, Riccardi G, et al. Prion disease in dromedary camels, Algeria. Emerg Infect Dis. 2018 June. https://doi.org/10.3201/ eid2406.172007 DOI: 10.3201/eid2406.172007 Abstract -------- Prions cause fatal and transmissible neurodegenerative diseases, including Creutzfeldt-Jakob disease in humans, scrapie in small ruminants, and bovine spongiform encephalopathy (BSE). After the BSE epidemic, and the associated human infections, began in 1996 in the United Kingdom, general concerns have been raised about animal prions. We detected a prion disease in dromedary camels (_Camelus dromedarius_) in Algeria. Symptoms suggesting prion disease occurred in 3.1 percent of dromedaries brought for slaughter to Ouargla abattoir in [2015-2016]. We confirmed diagnosis by detecting pathognomonic neurodegeneration and disease-specific prion protein (PrPSc) in brain tissues from 3 symptomatic animals. Prion detection in lymphoid tissues is suggestive of the infectious nature of the disease. PrPSc biochemical characterization showed differences with BSE and scrapie. Our identification of this prion disease in a geographically widespread livestock species requires urgent enforcement of surveillance and assessment of the potential risks to human and animal health. -- Communicated by: ProMED-mail < promed@promedmail.org > [The following excerpts from the discussion chapter of the paper add essential background, insights and conclusions: "We describe a prion disease in dromedary camels, designated as CPD, that we detected during routine antemortem inspection at the Ouargla slaughterhouse in Algeria. Retrospective analysis indicated a 3.1 percent prevalence of animals with neurologic signs suggestive of the disease in dromedaries brought for slaughter. That figure appears to be reliable given that clinical suspicion was confirmed in all 3 animals undergoing laboratory analysis. However, because prion diseases are characterized by long incubation periods and the age at which the disease becomes apparent (8 years and older) is more advanced than the age at which most dromedaries are slaughtered (up to 5 years), the prevalence found in the older animals is probably higher than the actual prevalence (excluding younger animals). "The spectrum of animal species susceptible to prion disease is large. However, only in ruminants belonging to the Bovidae and Cervidae families do prion diseases behave as infectious and naturally occurring conditions [felines were infected by the consumption of BSE-contaminated food. - mod.AS]. Dromedaries are not ruminants (suborder Ruminantia) but rather Tylopoda, a suborder of Artiodactyla, which also includes the 2-humped camel (_Camelus bactrianus_), wild Bactrian camel (_C. ferus_), llamas (_Lama glama_), alpacas (_Vicugna pacos_), and vicuñas (_V. vicugna_). The presence of a prion disease in dromedaries extends the spectrum of animal species naturally susceptible to prion diseases to taxa different from those already known and opens up new research areas on the ecology and the host-pathogen relationship of prion diseases. "Whether CPD is an infectious disease in natural conditions is a key question. In scrapie and CWD, in which lymphoid tissues are extensively involved, the horizontal transmission in natural conditions is efficient. In contrast, when the peripheral lymphoid tissues are not substantially involved, as in cattle BSE, atypical/Nor98 scrapie, and most human prion diseases, the horizontal transmission appears to be inefficient. This inefficiency usually is explained by assuming the in vivo dissemination of PrPSc to periphery as a prerequisite to facilitate prion shedding into the environment. Although we obtained samples from a single animal, our detection of PrPSc in all lymph nodes available suggests an abundant extraneural pathogenesis and, along with the notable prevalence of clinical cases at slaughterhouse, concurs to suggest the infectious nature of CPD. These observations also suggest that the disease has an acquired rather than spontaneous onset. "The origin of CPD is unknown. It might be a disease unique to dromedaries or a malady deriving from transmission of a prion disease from another species. It is worth noting that meat and bone meal has been exported from the United Kingdom worldwide, and after the ban of feeding animals with ruminant protein in 1988, export to the Third World had soared to 30 000 tons in 1991. Thus, the possibility that BSE-infected feed could have reached North Africa cannot be ruled out. However, even if the risk for BSE has not been formally assessed in Algeria and an official surveillance system for animal prion diseases is lacking, BSE is unlikely to appear in dromedaries without evidence in cattle populations. Moreover, dromedaries are mostly raised with no use of feedstuff. Lastly, the PrPSc biochemical signature in CPD clearly differs from that of BSE or sheep-passaged BSE. Although host factors are known to be able to alter the PrPSc signature during interspecies transmission, the BSE profile generally has been preserved in species accidentally or experimentally affected. In principle, CPD also might have derived from scrapie. Dromedaries often are raised along with sheep and goats, sharing common pastures. However, although the absence of an effective surveillance system prevents drawing any conclusion, scrapie has never been reported in Algeria, and a field survey in northeastern Algeria could not provide evidence of the disease. Moreover, the PrPSc signature of CPD differed from the classical scrapie case used for comparison. To contribute to clarify the origin and nature of CPD, bioassays in a panel of rodent models are ongoing for a thorough prion strain characterization. "Future investigations of the geographic distribution of CPD will help clarify its origin. If the disease is confined to the dromedary populations of Ouargla region, a localized event of transmission could be hypothesized. Common-source scrapie epidemics in sheep and goats occurred in the United Kingdom and Italy as a consequence of the use of accidentally contaminated vaccines. However, in the Ouargla region, no vaccination program has been implemented for infectious disease prophylaxis in dromedaries. Intriguingly, dromedary breeders indicate that the only food source other than pasture available to dromedaries in the Ouargla region are the waste dumps widespread in the desert near the oil extraction plants, where dromedaries and small ruminants gather and scavenge. The possibility that dromedaries acquired the disease from eating prion-contaminated waste needs to be considered. "Tracing the origin of prion diseases is challenging. In the case of CPD, the traditional extensive and nomadic herding practices of dromedaries represent a formidable factor for accelerating the spread of the disease at long distances, making the path of its diffusion difficult to determine. Finally, the major import flows of live animals to Algeria from Niger, Mali, and Mauritania should be investigated to trace the possible origin of CPD from other countries. "Camels are a vital animal species for millions of persons globally. The world camel population has a yearly growth rate of 2.1 percent. In 2014, the population was estimated at ˜28 million animals, but this number is probably underestimated. Approximately 88 percent of camels are found in Africa, especially eastern Africa, and 12 percent are found in Asia. Official data reported 350 000 dromedaries in Algeria in 2014. "On the basis of phenotypic traits and sociogeographic criteria, several dromedary populations have been suggested to exist in Algeria. However, recent genetic studies in Algeria and Egypt point to a weak differentiation of dromedary population as a consequence of historical use as a cross-continental beast of burden along trans-Saharan caravan routes, coupled with traditional extensive/nomadic herding practices. "Such genetic homogeneity also might be reflected in the Prion protein gene (PRNP). Studies on PRNP variability in camels are therefore warranted to explore the existence of genotypes resistant to CPD, which could represent an important tool for CPD management as it was for breeding programs for scrapie eradication in sheep. "In the past 10 years, the camel farming system has changed rapidly, with increasing set-up of periurban dairy farms and dairy plants and diversification of camel products and market penetration. This evolution requires improved health standards for infectious diseases and, in light of CPD, for prion diseases. "The emergence of another prion disease in an animal species of crucial importance for millions of persons worldwide makes it necessary to assess the risk for humans and develop evidence-based policies to control and limit the spread of the disease in animals and minimize human exposure. The implementation of a surveillance system for prion diseases would be a 1st step to enable disease control and minimize human and animal exposure. Finally, the diagnostic capacity of prion diseases needs to be improved in all Africa countries where dromedaries are part of the domestic livestock." OIE's updated list of notifiable animal diseases includes 2 Transmissible spongiform encephalopathies (TSE's), namely BSE (in Bovidae) and scrapie (in Caprinae). According to Algeria's most recent available annual report (2016), both are notifiable. BSE is listed among the diseases which have never been reported. Scrapie is listed among the diseases which were "absent in 2016;" its last occurrence "unknown." For both diseases, "no surveillance" applied. The final version of the above paper, to be published in the June 2018 edition of EID, will include 3 video clips. A map of Ouargla, Ouargla, Algeria: http://healthmap.org/ promed/p/28762 . - Mod.AS] |