Camel tuberculosis--a case report

Systematic review and meta-analysis of tuberculosis in animals in Nigeria

Animal tuberculosis (TB) is a contagious and chronic disease caused by mycobacteria belonging to theMycobacterium tuberculosis complex (MTBC) in domestic and wild animals. MTBC strains infection has been confirmed in many animal species in Nigeria, including captive wildlife, cattle, dromedary camels, goats, and pigs. Despite widespread infection and the potential impact of the disease on public health, active surveillance and control strategies are absent in Nigeria. This study aimed to conduct the first comprehensive meta-analysis to assess the distribution of tuberculosis and analyze the potential moderators of infection in animals in Nigeria. Eligible studies (sixty-one (Cadmus et al., 2014) [61] prevalence and seven (Menzies and Neill, 2000) [7] case reports) were retrieved and included in the analysis. The analyses showed an overall pooled TB prevalence of 7.0% (95% CI: 6.0-8.0) comprising of infection distributed in cattle (8.0%, 95% CI: 7.0-8.0), goats (0.47%, 95% CI: 0-1.2), sheep (0.27%, 95% CI: 0.14-0.46), camels (13.0%, 95% CI: 0-47), and wildlife (13.0%, 95% CI: 9-16) respectively. The occurrence of infection was significantly moderated by the publication periods, geographical location, sample size, and detection methods. TB prevalence was heterogeneous across several predictors, with the year of publication exhibiting a higher rate (46%) of the detected heterogeneity. These findings should provide policy-relevant information to guide the design and establishment of prevention and control measures amenable to the local situations in Nigeria.

Tuberculosis caused by Mycobacterium caprae in a camel (Camelus dromedarius)

BACKGROUND

Animal tuberculosis (TB) is distributed worldwide and has a wide range of wild and domestic reservoirs. Few studies concerning TB in camelids have been published in the last decade, particularly as regards Old World Camelids (OWC), but the increase in reports of TB outbreaks in these species in recent years suggests a high susceptibility to the infection.

CASE PRESENTATION

We studied a dromedary camel (Camelus dromedarius) herd (n = 24) in which a Mycobacterium caprae infection was detected. The TB infection was confirmed in one animal at necropsy through the detection of TB lesions, mainly in the abdominal organs, and the subsequent isolation of M. caprae (SB0157 spoligotype). The whole herd was additionally tested using cellular and humoral based diagnostic techniques. The intradermal tuberculin test results were compared with those obtained using P22 ELISA for the detection of specific antibodies against the M. tuberculosis complex. The TB infected animal was a positive reactor to both the intradermal tuberculin tests and P22 ELISA, while the others were negative to all the diagnostic tests.

CONCLUSION

The present study found M. caprae infection in OWC. This is the first report of M. caprae infection in an OWC not living in a zoo. Since the animal was born in the herd and fed with goat's milk, this practice was suspected to be the potential source of TB infection, which was not confirmed in the other animals present in the herd. Moreover, our results highlight that the intradermal tuberculin test and the P22 ELISA could be valuable tools for the diagnosis of TB in OWC.

Coxiella burnetii in Dromedary Camels (Camelus dromedarius): A Possible Threat for Humans and Livestock in North Africa and the Near and Middle East?

The "One Health" concept recognizes that human health is connected to animal health and to the ecosystems. Coxiella burnetii-induced human Q fever is one of the most widespread neglected zoonosis. The main animal reservoirs responsible for C. burnetii transmission to humans are domesticated ruminants, primarily goats, sheep, and cattle. Although studies are still too sparse to draw definitive conclusions, the most recent C. burnetii serosurvey studies conducted in herds and farms in Africa, North Africa, Arabian Peninsula, and Asia highlighted that seroprevalence was strikingly higher in dromedary camels (Camelus dromedarius) than in other ruminants. The C. burnetii seroprevalence in camel herds can reach more than 60% in Egypt, Saudi Arabia, and Sudan, and 70 to 80% in Algeria and Chad, respectively. The highest seroprevalence was in female camels with a previous history of abortion. Moreover, C. burnetii infection was reported in ticks of the Hyalomma dromedarii and Hyalomma impeltatum species collected on camels. Even if dromedary camels represent <3% of the domesticated ruminants in the countries of the Mediterranean basin Southern coast, these animals play a major socioeconomic role for millions of people who live in the arid zones of Africa, Middle East, and Asia. In Chad and Somalia, camels account for about 7 and 21% of domesticated ruminants, respectively. To meet the growing consumers demand of camel meat and milk (>5 million tons/year of both raw and pasteurized milk according to the Food and Agriculture Organization) sustained by a rapid increase of population (growth rate: 2.26-3.76 per year in North Africa), dromedary camel breeding tends to increase from the Maghreb to the Arabic countries. Because of possible long-term persistence of C. burnetii in camel hump adipocytes, this pathogen could represent a threat for herds and breeding farms and ultimately for public health. Because this review highlights a hyperendemia of C. burnetii in dromedary camels, a proper screening of herds and breeding farms for C. burnetii is urgently needed in countries where camel breeding is on the rise. Moreover, the risk of C. burnetii transmission from camel to human should be further evaluated.

BCG vaccination for bovine tuberculosis; conclusions from the Jerusalem One Health workshop

The global burden of bovine tuberculosis (bTB) remains poorly characterized, with spill-over impacts on multiple species. The "One Health" concept is especially relevant given the bidirectional risk of cattle infecting humans with Mycobacterium bovis and humans infecting cattle with Mycobacterium tuberculosis. "Test and cull" is the traditional bTB control method, but the strategy may not be economically feasible or culturally acceptable where cattle are highly prized or their killing is a religious taboo; it is also less effective when there are wildlife reservoirs of infection. Vaccination with M. bovis bacille Calmette-Guerin (BCG) provides protection against bTB, but its use in animals has been limited. The Jerusalem One Health workshop considered key bTB knowledge gaps and innovative solutions. Knowledge gaps identified included (a) the poorly quantified prevalence of M. bovis infection and disease in cattle, domestic camelids and human populations in developing countries, (b) the absence of alternatives to a "test and cull" strategy in settings where the killing of infected animals is culturally or economically unacceptable, or where affected species are protected and (c) an understanding of the induction of mucosal immunity against bTB. We summarize discussions on the use of BCG vaccination in domestic animals and wildlife and list potential projects to address the knowledge gaps identified.

Tuberculosis in dromedary camels slaughtered in Nigeria: a documentation of lesions at postmortem

In comparison with other livestock, tuberculosis (TB) in camels has not been extensively studied in Nigeria. Camels in the hands of Nigerian pastoralists share the livestock ecosystem and are increasingly becoming an important component of the sector. This study was designed to investigate the occurrence of TB lesions and animal-level risk of infection in slaughtered camel carcasses in one of the public abattoirs in Nigeria, from June to August 2016. A total of 212 camel carcasses comprising 82.5% (175/212) males and 17.5% (37/212) females were examined for tuberculous lesions. Of the carcasses examined, 33.5% (71/212) had TB lesions. The occurrence of lesions was most significantly associated with poor body condition (OR = 0.249; CI 0.134-0.454 [p < 0.001]). Distribution among anatomical sites of macroscopic lesions in the infected camels revealed three different pathological patterns as pulmonary (n = 51), abdominal (n = 11), and disseminated (n = 9) forms. Higher prevalence of gross TB lesions in camel carcasses highlights eminent threats to both animal and public health, pointing to an already existing risk of intra- and inter-species transmission of infection.

Prevalence of bovine tuberculosis in cattle, goats, and camels of traditional livestock raising communities in Eritrea

Background

The aim of the current study was to assess the prevalence of bovine tuberculosis (BTB) in cattle, goats, and camels, and its zoonotic potential within the traditional livestock raising communities in four regions of Eritrea. The Single Intradermal Comparative Tuberculin Test (SICTT) as indicator of M. bovis infection was conducted on 1077 cattle, 876 goats, and 195 camels. To elucidate possible risk factors for BTB transmission between animals and its potential zoonotic implication, questionnaire based face-to-face interviews were conducted in households of which 232 raised cattle, 128 goats, and 29 camels.

Results

The results of the SCITT were interpreted using the OIE standard (> 4 mm cut-off) for positive responses. In cattle, individual animal (n = 1077) and herd (n = 413) prevalences were 1.2% (n = 13) [Confidence Interval (CI) 95% CI, 1.0–1.3%] and 3.2% (n = 13) (95% CI, 3.0–3.4%), respectively. In goats (n = 876), none of the animals was positive. In camels, individual animal (n = 195) and herd (n = 70), BTB prevalences were 1.5% (n = 3) (95% CI,1.4–1.6%) and 2.9(n = 2) (95% CI, 0.9–4.6%), respectively. Overall, male animals were more at risk (OR = 2.6; 95% CI:1.0–8.7) when compared to females. Sharing of water points, introduction of new animals into herds and migration of animals over large distances were common events that may contribute to intra and inter-species transmission of BTB. Consumption of raw milk, lack of BTB transmission awareness, and low levels of education were common in the farming communities.

Conclusion

The current study highlighted a low prevalence of M. bovis in cattle, goats and camels in extensive traditional livestock in Eritrea. Despite this, the spatial distribution of affected animals across most of the sampled regions and consumption of unpasteurized milk warrants surveillance, cautious and timely control measures for the disease.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1397-0) contains supplementary material, which is available to authorized users.

Diagnostic value of animal-side antibody assays for rapid detection of Mycobacterium bovis or Mycobacterium microti infection in South American camelids

Tuberculosis (TB) in South American camelids (SAC) is caused by Mycobacterium bovis or Mycobacterium microti. Two serological methods, rapid testing (RT) and the dual-path platform (DPP) assay, were evaluated using naturally infected SAC. The study population included 156 alpacas and 175 llamas in Great Britain, Switzerland, and the United States. TB due to M. bovis (n = 44) or M. microti (n = 8) in 35 alpacas and 17 llamas was diagnosed by gross pathology examination and culture. Control animals were from herds with no TB history. The RT and the DPP assay showed sensitivities of 71% and 74%, respectively, for alpacas, while the sensitivity for llamas was 77% for both assays. The specificity of the DPP assay (98%) was higher than that of RT (94%) for llamas; the specificities of the two assays were identical (98%) for alpacas. When the two antibody tests were combined, the parallel-testing interpretation (applied when either assay produced a positive result) enhanced the sensitivities of antibody detection to 89% for alpacas and 88% for llamas but at the cost of lower specificities (97% and 93%, respectively), whereas the serial-testing interpretation (applied when both assays produced a positive result) maximized the specificity to 100% for both SAC species, although the sensitivities were 57% for alpacas and 65% for llamas. Over 95% of the animals with evidence of TB failed to produce skin test reactions, thus confirming concerns about the validity of this method for testing SAC. The findings suggest that serological assays may offer a more accurate and practical alternative for antemortem detection of camelid TB.

Pathology of camel tuberculosis and molecular characterization of its causative agents in pastoral regions of Ethiopia

A cross sectional study was conducted on 906 apparently healthy camels slaughtered at Akaki and Metehara abattoirs to investigate the pathology of camel tuberculosis (TB) and characterize its causative agents using postmortem examination, mycobacteriological culturing, and multiplex polymerase chain reaction (PCR), region of difference-4 (RD4)-based PCR and spoligotyping. The prevalence of camel TB was 10.04% (91/906) on the basis of pathology and it was significantly higher in females (χ² = 4.789; P = 0.029). The tropism of TB lesions was significantly different among the lymph nodes (χ² = 22.697; P = 0.002) and lung lobes (χ² = 17.901; P = 0.006). Mycobacterial growth was observed in 34% (31/91) of camels with grossly suspicious TB lesions. Upon further molecular characterization using multiplex PCR, 68% (21/31) of the colonies showed a positive signal for the genus Mycobacterium, of which two were confirmed Mycobacterium bovis (M. bovis) by RD4 deletion typing. Further characterization of the two M. bovis at strains level revealed that one of the strains was SB0133 while the other strain was new and had not been reported to the M. bovis database prior to this study. Hence, it has now been reported to the database, and designated as SB1953. In conclusion, the results of the present study have shown that the majority of camel TB lesions are caused by mycobacteria other than Mycobacterium tuberculosis complex. And hence further identification and characterization of these species would be useful towards the efforts made to control TB in camels.