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Investigation of the high rates of extrapulmonary tuberculosis in Ethiopia reveals no single driving factor and minimal evidence for zoonotic transmission of Mycobacterium bovis infection.

Berg S, Schelling E, Hailu E, Firdessa R, Gumi B, Erenso G, Gadisa E, Mengistu A, Habtamu M, Hussein J, Kiros T, Bekele S, Mekonnen W, Derese Y, Zinsstag J, Ameni G, Gagneux S, Robertson BD, Tschopp R, Hewinson G, Yamuah L, Gordon SV, Aseffa A - BMC Infect. Dis. (2015)

Bottom Line: However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN.High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024).The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

View Article: PubMed Central - PubMed

Affiliation: Animal and Plant Health Agency, TB Research Group, New Haw, Addlestone, Surrey, KT15 3NB, UK. stefan.berg@apha.gsi.gov.uk.

ABSTRACT

Background: Ethiopia, a high tuberculosis (TB) burden country, reports one of the highest incidence rates of extra-pulmonary TB dominated by cervical lymphadenitis (TBLN). Infection with Mycobacterium bovis has previously been excluded as the main reason for the high rate of extrapulmonary TB in Ethiopia.

Methods: Here we examined demographic and clinical characteristics of 953 pulmonary (PTB) and 1198 TBLN patients visiting 11 health facilities in distinct geographic areas of Ethiopia. Clinical characteristics were also correlated with genotypes of the causative agent, Mycobacterium tuberculosis.

Results: No major patient or bacterial strain factor could be identified as being responsible for the high rate of TBLN, and there was no association with HIV infection. However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN. Among PTB patients, those infected with Lineage 4 reported "contact with other TB patient" more often than patients infected with Lineage 3 did (OR = 1.6, CI 95% 1.0-2.7; p = 0.064). High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024). On the other hand, TBLN cases infected with Lineage 4 tended to get milder symptoms overall for the constitutional symptoms than those infected with Lineage 3.

Conclusions: The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

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Related in: MedlinePlus

Mapping of collection sites and extrapulmonary TB in Ethiopia. Information received from the Federal Ministry of Health (FMoH), Ethiopia.
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Fig1: Mapping of collection sites and extrapulmonary TB in Ethiopia. Information received from the Federal Ministry of Health (FMoH), Ethiopia.

Mentions: Ethiopia, with a population of over 90 million people, is among the countries with the highest TB burdens in the world, with an incidence rate of 247 per 100,000 in 2012 [1]. Moreover, Ethiopia has reported a higher than average incidence of extrapulmonary TB since records started in the 1990s. What are the risk factors that can explain this high rate of extrapulmonary TB in Ethiopia? More than 80% of all extrapulmonary cases involve cervical TB lymphadenitis that currently accounts for around 33% of all incident TB cases in the country, with a prevalence that roughly increases from 20% to 45% along a south to north geographic axis (data from Ethiopian Federal Ministry of Health; Figure 1). In parallel, Ethiopia is home to the largest livestock population in Africa with ~52 million cattle [6], and more than 80% of the labour force works in the agricultural sector. As several investigations have shown that bovine TB is endemic in Ethiopian cattle [7,8] and reaches high prevalence in regions with intensive husbandry systems [9-11], it would seem plausible that zoonotic transmission of M. bovis would have an influence on the prevalence of TBLN in the country. However, in a large nation-wide molecular epidemiology study [12] we explored the public health risk for zoonotic TB in Ethiopia and concluded that the overall role of M. bovis as a causative agent of TB in humans was approximately only 1%. This led us to conclude that the high incidence rate of extrapulmonary TB reported in Ethiopia is likely due to other factors.Figure 1


Investigation of the high rates of extrapulmonary tuberculosis in Ethiopia reveals no single driving factor and minimal evidence for zoonotic transmission of Mycobacterium bovis infection.

Berg S, Schelling E, Hailu E, Firdessa R, Gumi B, Erenso G, Gadisa E, Mengistu A, Habtamu M, Hussein J, Kiros T, Bekele S, Mekonnen W, Derese Y, Zinsstag J, Ameni G, Gagneux S, Robertson BD, Tschopp R, Hewinson G, Yamuah L, Gordon SV, Aseffa A - BMC Infect. Dis. (2015)

Mapping of collection sites and extrapulmonary TB in Ethiopia. Information received from the Federal Ministry of Health (FMoH), Ethiopia.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4359574&req=5

Fig1: Mapping of collection sites and extrapulmonary TB in Ethiopia. Information received from the Federal Ministry of Health (FMoH), Ethiopia.
Mentions: Ethiopia, with a population of over 90 million people, is among the countries with the highest TB burdens in the world, with an incidence rate of 247 per 100,000 in 2012 [1]. Moreover, Ethiopia has reported a higher than average incidence of extrapulmonary TB since records started in the 1990s. What are the risk factors that can explain this high rate of extrapulmonary TB in Ethiopia? More than 80% of all extrapulmonary cases involve cervical TB lymphadenitis that currently accounts for around 33% of all incident TB cases in the country, with a prevalence that roughly increases from 20% to 45% along a south to north geographic axis (data from Ethiopian Federal Ministry of Health; Figure 1). In parallel, Ethiopia is home to the largest livestock population in Africa with ~52 million cattle [6], and more than 80% of the labour force works in the agricultural sector. As several investigations have shown that bovine TB is endemic in Ethiopian cattle [7,8] and reaches high prevalence in regions with intensive husbandry systems [9-11], it would seem plausible that zoonotic transmission of M. bovis would have an influence on the prevalence of TBLN in the country. However, in a large nation-wide molecular epidemiology study [12] we explored the public health risk for zoonotic TB in Ethiopia and concluded that the overall role of M. bovis as a causative agent of TB in humans was approximately only 1%. This led us to conclude that the high incidence rate of extrapulmonary TB reported in Ethiopia is likely due to other factors.Figure 1

Bottom Line: However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN.High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024).The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

View Article: PubMed Central - PubMed

Affiliation: Animal and Plant Health Agency, TB Research Group, New Haw, Addlestone, Surrey, KT15 3NB, UK. stefan.berg@apha.gsi.gov.uk.

ABSTRACT

Background: Ethiopia, a high tuberculosis (TB) burden country, reports one of the highest incidence rates of extra-pulmonary TB dominated by cervical lymphadenitis (TBLN). Infection with Mycobacterium bovis has previously been excluded as the main reason for the high rate of extrapulmonary TB in Ethiopia.

Methods: Here we examined demographic and clinical characteristics of 953 pulmonary (PTB) and 1198 TBLN patients visiting 11 health facilities in distinct geographic areas of Ethiopia. Clinical characteristics were also correlated with genotypes of the causative agent, Mycobacterium tuberculosis.

Results: No major patient or bacterial strain factor could be identified as being responsible for the high rate of TBLN, and there was no association with HIV infection. However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN. Among PTB patients, those infected with Lineage 4 reported "contact with other TB patient" more often than patients infected with Lineage 3 did (OR = 1.6, CI 95% 1.0-2.7; p = 0.064). High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024). On the other hand, TBLN cases infected with Lineage 4 tended to get milder symptoms overall for the constitutional symptoms than those infected with Lineage 3.

Conclusions: The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

Show MeSH
Related in: MedlinePlus