Mapping of the distribution of Mycobacterium bovis strains involved in bovine tuberculosis in Mozambique

[摘要] ENGLISH ABSTRACT: Bovine tuberculosis (BTB), caused by bacteria of the Mycobacterium tuberculosis complex isreported to cause economic and public health negative impact in countries where it is prevalent.The control of the disease has been a difficult task worldwide.The main object of this thesis was to use molecular tools to generate useful information tocontribute to the design of appropriate BTB control measures in Mozambique. To do so weconsidered a deep knowledge of the BTB history in Mozambique to be essential. The searchwas largely based on the reports produced annually by the Veterinary Services and otheravailable information. We found reports of BTB in Mozambique as early as 1940. These caseswere mainly identified as a result of post-mortem meat inspection. The higher numbers of casesreported were from 8 locations, namely Maputo, Magude, Vilanculos, Beira, Chimoio, Tete,Quelimane and Nampula, and served as a basis to decide the locations to perform prevalenceand molecular epidemiologic studies. Prevalence studies were done in 10 districts selected based on the history of a high number ofBTB case reports (intentionally biased towards locations presumably with higher prevalence),a high cattle density, but also to represent districts from the south, centre and north ofMozambique. A representative sample was defined, based on all livestock areas or villages inMassingir and Govuro Districts or by randomly selecting small-scale and commercial herds in8 districts, specifically Manhiça, Chibuto, Buzi, Gondola, Mutarara, Mogovolas, Angoche andMecanhelas. Results were obtained from 6983 cattle tested using tuberculin testing. Apparentprevalence varied from 0.98% in Massingir to 39.6% in the Govuro, with prevalence as highas 71.4% in some livestock areas/herds. The analysis of risk factors showed no noteworthydifference with respect to the sex of the animal. Younger age had significantly lower odds ofinfection compared to the older age class. There was a tendency of cattle from small-scale herdsto have lower prevalence when compared to the commercial herds. From the prevalence studies, 187 tissue and 41 milk samples from BTB reactors were collected.Additionally 220 tissue samples were obtained from the Central Veterinary Laboratory routinediagnostic work. Samples were subject to bacteriological culture and a collection of 170 M.bovis isolates were obtained. Eight additional isolates were supplied from another study. Allisolates were subjected to molecular typing using spoligotyping, and a sub-sample usingMIRU-VNTR and regions of difference (RD) analysis. Fifteen different spoligotype patterns were identified of which 8 were not previously registered in the Mbovis.org database. Thepattern SB0961 accounted for 61% of the isolates and was found in all areas of the countryinvestigated. We hypothesize that this was one of the first clones to be introduced inMozambique. Twenty-nine isolates had the pattern SB0140, which is specific for the European1 (Eu1) clonal complex. Eleven isolates with this spoligotype were subjected to RD analysis,and all isolates had the Eu1 specific deletion. These were all isolated from cattle from the southof Mozambique and the majority from commercial farms that imported cattle, mainly fromSouth Africa, where the Eu1 clonal complex is common. There were no isolates of the African1 (Af1) or African 2 (Af2) clonal complexes that are frequent in Central-West Africa and EastAfrica, respectively. The clones identified from different farms and districts, strongly suggestroutes of transmission and/or common source of infection.In conclusion, our results show a potential increase in the prevalence of BTB in Mozambiqueeven taking into consideration i) that the selection of locations in our study was biased towardslocations with a history of higher BTB prevalence and ii) the use of a more sensitive techniquei.e. the testing in the middle neck region as opposed to the testing in the caudal fold as used inprevious studies.Even if no cattle to human transmission was found in studies done in Mozambique so far, theevidence of M. bovis shedding through milk and the lack of correct practices to prevent animalto human transmission (consumption of raw milk), strongly suggests that there is zoonotic risk;a subject that needs to be investigated. The results presented in this work also strengthen the need to reinforce the current regulationsthat require a negative BTB test result before cattle importation. The same should be enforcedfor the internal movements, as the frequency of shared genotypes (Spoligotype and MIRU)from cattle originating from different parts of the country strongly suggest intra-contrytransmission of BTB.

[发布机构] Stellenbosch University