Survey of Bovine Tuberculosis in Slaughtered Cattle in Gusau Abattoir, Zamfara State, Nigeria

Survey of Bovine Tuberculosis in Slaughtered Cattle in Gusau Abattoir, Zamfara State, Nigeria

CHAPTER ONE

Objectives of the Study

To determine the prevalence of bovine tuberculosis in slaughtered cattle at Gusau abattoir using detection methods (Postmortem examination, Ziehl- Neelsen staining/microscopy and RD deletiontyping).
To determine the risk factors among Professionals working with animals and general public on bovine tuberculosis.

CHAPTER TWO

LITERATURE REVIEW

Historical Perspective of Bovine Tuberculosis

It has been assumed for a long time that human tuberculosis had its origin as a zoonosis, with M. tuberculosis evolving from Mycobacterium bovis by specific adaptation of an animal pathogen to the human host at the time of cattle domestication 10,000 to 15,000 years ago (de la Rua-Domenech, 2006). However, deletion analysis ofMycobacterium tuberculosis complex(MTC) strains isolated in 30 countries and the recent sequencing of the M. bovis genome have shown the genome of M. bovis to be smaller than that of

tuberculosis (Brosch et al., 2002; Garnier et al., 2003). It now appears that M. bovis is the final member of a separate lineage of bacteria (represented by M. africanum, M. microti and M. bovis) that branched from the common ancestor of the MTC when members of this complex were already human pathogens (de la Rua-Domenech, 2006). By contrast, modern strains of M. tuberculosis would constitute a separate lineage that emerged approximately 35,000 years ago, before the M. bovis lineage, and are thus philogenetically closer to the common progenitor of the MTC (Brosch et al., 2002; Garnier et al., 2003).

It is presumed that the genus Mycobacterium originated more than 150 million years ago (Daniel, 2006). Mycobacterium tuberculosis was thought to have co-evolved with early hominids in East Africa in about 3 million years ago, the modern members of M. tuberculosis complex seem to have originated from a common progenitor about 15,000- 35,000 years ago (Gutierrez et al., 2005).Historically, taxonomic segregation of the Mycobacterium tuberculosis complex (MTC) has been based upon each species‘ unique combination of growth, morphological, physiological and biochemical characteristics (Niemann et al., 2000). Variation in geographical distribution, host preference, virulence, and relative human infectivity also differentiate the tubercle bacilli (Huard et al., 2003). The understanding of genetic variability within the MTC is ever increasing, and genetic criteria are now routinely used to identify veterinary isolates to the species level and fingerprint them (Barnes and Cave, 2003). The MTC is generally considered a family of ―ecotypes‘‘ of very closely related Mycobacteria, with each ecotype being adapted to cause tuberculosis disease in a specific host species or group, even though inter-species transmission can occur (Smith et al., 2006a). In contrast to the earlier hypothesis that tuberculosis has evolved from an originally animal disease to a human disease (Diamond, 2002), new findings indicated that, in fact, tuberculosis first emerged in humans and was subsequently transmitted to animals (Wirth et al., 2008). Recent studies suggest that the common ancestor of the Mycobacterium tuberculosis complex emerged from its progenitor perhaps 40,000 years ago in East Africa. Some 10,000 to 20,000 years later, two independent clades evolved, one resulting in M. tuberculosis lineages in humans, while the other spread from humans to animals, resulting in the diversification of its host spectrum and formation of other M. tuberculosis complex member species, including Mycobacterium bovis (Gutierrez et al., 2005; Wirth et al., 2008). This adaptation to animal hosts probably coincided with the domestication of livestock approximately 13,000 years ago (Michel et al., 2010).

CHAPTER THREE

MATERIALS AND METHODS

Study Area

Gusau abattoir is located in Gusau Local Government Area, capital of Zamfara State, and is one Kilometer Northwest of Gusau town. It is administered by the State Ministry of Animal Health and Livestock Development, and was established to provide slaughter and meat inspection services to local butcher shops in the town. It is the only source of inspected beef in town, and to the neighboring Local Government Areas like Bungudu, Maru and Tsafe. Gusau is located between latitude 11°53‘^N and longitude 06°39‘^E, and occupies an area of 3,364km² (Topographic-sheet, 1990). Based on the results of 2006 National Population Census, Gusau Local Government Area had a population of about 383,162 people (NPC, 2006).

Zamfara State comprises of fourteen (14) Local Government Areas and has an estimated population of 3,259,846 people according to 2006 Census figures from the National Population Commission(NPC, 2006; ZASIDEP, 2007). About 82% of the population in the State are engaged in Agriculture with most farming families also owning livestock (ZASIDEP, 2007). Zamfara State is bordered in the North by Niger Republic, to the East by Katsina State, to the West by Sokoto State, to the South by Kaduna, Niger and Kebbi States. It is located within latitudes 10°52‘^N to 13°10‘^N and longitudes 04°40‘^E to 07°10‘^E (ZASIDEP, 2007). The State has an estimated animal population of: 3,190,010 Cattle, 34,796 Camels, 5, 177,348 Goats and 4, 933,304 Sheep (MAHLD, 2011).

CHAPTER FOUR RESULTS

Prevalence of Bovine Tuberculosis

Prevalence of bovine tuberculosis by postmortem findings

Gross lesions typical of bovine tuberculosis (Plates I and II) were detected in 226(6.12%) of the cattle slaughtered during the study period. Most of the encountered organs/tissues with lesions were enlarged, with number of yellowish granulomas or tubercles, some with cheese-like foci on cut-surface (Plates I and II). The tuberculous- like lesions were observed in eleven different tissues/organs from carcasses (Table 4.1). These included lesions in 90 (2.4%) lungs, 76 (2.1%) livers, 16 (0.4%) tracheo-bronchial lymphnodes, 13 (0.4%) mesenteric lymphnodes, 9 (0.2%) prescapular lymphnodes, 8 (0.2%) hearts and 4 (0.1%) spleen samples. Suspected tuberculous lesions were also observed in 3 (0.1%) each of kidneys, mammary glands, pleura, and 1 (0.02%) small intestines. The distribution and occurrence of tuberculous like lesions in different anatomical sites is presented on Table 4.1. Yellowish granulomatous lesions and abscesses (containing yellowish pus) were observed most in 90 (2.4%) lungs compared with the least recorded in 1 (0.02%)small intestines.

CHAPTER FIVE

DISCUSSION

The prevalence of 6.1% was recorded based on detection of gross lesions in tissues and organs of slaughtered cattle by participatory meat inspection. It was similar to the slaughter-slabs prevalence of 4.7% reported by Hena et al. (2012) in Bakura Local Government Area of the same Zamfara State (Northwestern Nigeria). Moreover, it was similar to 4.5% prevalence reported by Cadmus et al. (2009) from Bodija Municipal Abattoir in Ibadan (Southwestern Nigeria) and 4.4% prevalence published by Damina et al. (2011) from Jos abattoir (Northcentral Nigeria). However, compared to the data obtained in other region of Nigeria, this finding was lower than the previous report of a retrospective study by Aliyu et al. (2009) that documented a relatively high prevalence rate in Gombe State at 12.3% (Northeastern Nigeria). But it was higher than the following abattoir-based studies recorded in other States, it includes: 1.1% prevalence from Maiduguri Borno State documented by Raufu and Ameh (2010) (Northeastern Nigeria) and 0.54% prevalence from Ogbomosho, Oyo State (Ameen et al., 2008) (Southwestern Nigeria). Also when compared with the data recorded elsewhere in Africa, the abattoir bovine TB prevalence recorded in this study was higher than 3.6% prevalence rate reported in Niger Republic (Boukary et al., 2011), 1.0% prevalence reported in Cameroon by Koro et al. (2013) and 2.5% reported in Ghana (Asante-Poku et al., 2014), but it was similar to the 7.3% prevalence of bovine tuberculosis based on the detection of suggestive macroscopic lesions in Chad Repulic (Diguimbaye-Djaibé et al., 2006). As asserted by Koro et al. (2013), these differences observed in rates could be intriguing because there is frequent cattle movement between these countries, which can lead to the strain dissemination and transmission of bovine tuberculosis. In addition, this result is consistent with the finding of Aylate et al. (2013) who recorded 6.1% prevalence in an abattoir-based study in Ethiopia.

CHAPTER SIX

CONCLUSION AND RECOMMENDATIONS

Conclusion

This study has for the first time in almost two decades since creation of Zamfara State in Northwestern Nigeria, used laboratory-based diagnostic techniques to investigate the prevalence of bovine TB infection; other than the subjective visual postmortem examination of suspected TB lesions. Results obtained have confirmed and established the prevalence of Mycobacterium bovis and other members of MTC group (Mycobacterium caprae and Mycobacterium tuberculosis) infections amongst cattle slaughtered in the study area.Mycobacteria were identifiedto the species level and that species prevalence rates were 88.2% for Mycobacterium bovis, 8.8% Mycobacterium caprae and 2.9% as Mycobacterium tuberculosis. This provides information on the species of Mycobacteria that could had been implicated in the often observed tuberculous-like lesions among cattle slaughtered in Gusau abattoir and elsewhere in Nigeria; which these findings would be useful for modifying and implementing TB control measures in the State and country at large.

Accordingly, the following are hereby suggested to be the recommendations:

There is the need for more study to determine the prevalence of bovine TB in other animal species in the State. Detailed epidemiological studies are needed to investigate the modes of transmission, risk factors of the disease, distribution of tuberculousMycobacterialspecies andstrains, and differential susceptibility to tuberculousMycobacteria amongst the indigenous cattle breeds and other domestic animals tended together as it is for most herdsin the State, as well as in humans.
There is the need to increase effort in thorough meat inspection with a view to reduce the possible incidence of the disease in humans. However, intensification and standardization of abattoir inspection protocols specially detailed meat inspection, establishment of enabling environment for an added confirmatory tests for bovine TB (e.g.: genomic analysis), enhanced training among staff, reviewing and enforcement of enacted laws governing meat inspection; such methods are recommended as essential and cost-effective interventions to improve bovine TB surveillance in Nigeria, with subsequent protection of animal and man
Moreover, in order to put this to check, restrictions in random movements of cattle herds should be imposed to minimize transmission of infection from diseased and in-contact to clean susceptible animals. Government should impose it as a policy: to register any sold-out animal along with its detailed records of all previous ownership(s) with address(es); this will make control at the abattoir easy to trace carcass(es) with bovine TB lesions back to their origins, and also imposeregular herd screening of cattle using tuberculin skin test for maximum

and accurate detection withthe consequent elimination of tuberculin positive reactors by segregation and phasing out of the infected animals. Quarantine measures should be regularly observed, especially for the trade cattle since Zamfara State shares border with the Niger Republic.

There is the need for public awareness on the role of bTB in animals and also TB amongst humans in the State. Although risk factors of bovine TB infection have been scarcely studied in the
Further studies on the risk factors of zoonotic TB transmission in humans require case-control studies on those persons with already established TB infection. However, before it is embark on the national bTB control program, an in depth knowledge of possible risk factors is an essential prerequisite and should, therefore, also include risk factors associated with the dominant animals management systems in the country, food hygiene, food preference and feeding habits amongst humans, the influence of the environment, cultures and common norms, and nutritional
Cattle professionals such as butchers, cattle handlers, cattle traders and meat sellers should be cautioned and enlightened on the dangers of infection, and should be enforced to adhere to the appropriate preventive measures. However, it should be made mandatory through Government-backed legislature the routine testing of butchers and other abattoir personnel for TB, and when tested positive; personnel should be banned from handling animals or being involved in animal related operations till his/her full recovery is

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