Epidemiology of brucellosis and Q fever in Togo and the risk of disease spread through cattle trade in West Africa

Zoonotic diseases account for more than half of infectious diseases of humans and three
quarters of all emerging infectious diseases. Most of this burden lies with poor, rural
communities who rely on livestock for nutrition and income. In order to advocate on
behalf of these communities and reduce the disease burden, there is a need for high
quality epidemiological data acquired through transdisciplinary approaches involving the
natural, health and social science fields.
Brucellosis is one of the most common zoonoses in the world. This bacterial disease has
a major impact on human health, livestock production and the economy. In recent years,
Q Fever has become a bacterial zoonosis of increasing interest, in part due to an
unprecedented, large-scale outbreak in the Netherlands in 2007-2010. However, there is
an absence of high quality epidemiological data from West Africa for both brucellois and
Q Fever.
Member countries of the Economic Community of West African States (ECOWAS) are
required to permit free movement of people and goods across borders. This mobility is
important culturally, socially and economically. However, mobile populations in sub-
Saharan Africa suffer from the least access to health services. Cross-border trade and
seasonal transhumance are central to livestock production to West Africa, but these
movements can facilitate the rapid spread of pathogens across large distances. The
Savannah Region of northern Togo is the country’s main livestock raising area. This is a
dynamic zone, with frequent movement of both people and livestock across its borders
with Ghana, Burkina Faso and Benin.
Aims
-To assess the global burden of human brucellosis and identify data gaps
-To provide the first data on the epidemiology of brucellosis and Q Fever in
people and animals in Togo
-To conduct the first quantitative assessment of cattle trade in Togo, including the
potential impact on disease spread in West Africa
-To assess the mobility of people and livestock and the access to health care and
other social services in northern Togo
-To foster intersectoral collaboration and transdisciplinarity in Togo
Methods
A systematic review and meta-analysis of the burden of human brucellosis was
undertaken in the framework of the Global Burden of Disease Study 2010. Additionally,
primary data collection was conducted in the Savannah Region of northern Togo. A
brucellosis and Q Fever serosurvey was conducted in cattle, sheep, goats and people in
25 randomly selected villages in 2011 and 18 transhumant herds from Burkina Faso in
2012. The serological testing methods included the Rose Bengal Test (RBT), Enzymelinked
Immunosorbent Assay (ELISA), Complement Fixation Test (CFT) and
Immunofluoresence Assay (IFA). Multiple Loci Variable Number of Tandem Repeats
Analysis (MLVA) was used to genotype Brucella strains isolated from bovine hygroma
fluid. Semi-structured interviews were conducted in 2011 in parallel with the serosurvey
to assess the mobility of the local population and their access to health care and other
social services. In 2012, semi-structured interviews were conducted with cattle traders in
the 9 principal cattle markets in the study zone. The data collected was used to simulate
cross-border livestock flows and assess the potential risk of disease spread in West
Africa through cattle trade.
Principal Findings
The systematic review quantified the severe and chronic impact of brucellosis on its
sufferers and provided the first informed estimates of acute and chronic disability
weights for brucellosis. Major knowledge gaps regarding the incidence of brucellosis are
evident for Sub-Saharan Africa, Eastern Europe, the Asia-Pacific, and Central and South
America.
In Togo, the association between cattle seropositivity and a history of abortion in cows
suggests that brucellosis and Q Fever have an important impact on livestock production.
Given the absence of small ruminants seropositive for brucellosis, it is likely that only B.
abortus, not B. melitensis, is circulating in the study zone. People of Fulani ethnicity
were shown to have greater exposure to zoonoses than the rest of the population,
suggesting that cultural factors may influence the disease epidemiology. These results represent the first epidemiological data for zoonoses in linked human and animal
populations in Togo. The impact of these diseases on human health and the economy
warrants further investigation.
The B. abortus strains isolated from cattle hygromas are among the first Brucella
genotypic data available from West Africa. The identification of three distinct strains from
only a small geographical area highlights the genetic diversity of circulating strains in the
study zone. The two deletions detected in the BruAb2_0186 gene have important
diagnostic and, possibly, epidemiological consequences. More molecular and
epidemiological data are needed from the region, in order to better understand
transmission patterns and develop more suitable diagnostic assays. The use of a
chaotrophic buffer to preserve and inactivate DNA was both a safer and more sensitive
diagnostic method than culture, and is of particular relevance to countries with poor
laboratory biosafety.
The first quantitive assessment of the risk of disease spread in West Africa through
cross-border cattle trade demonstrated that surveillance for emerging infectious
diseases as well as control activities targeting endemic diseases are likely to be
ineffective if only conducted at a national level. The trade network in northern Togo
extended into Burkina Faso, Ghana, Benin and Nigeria, with their epidemiological
systems likely to be intimately linked to one another. There is a need for greater
collaboration between countries at the regional level in order to strengthen disease
surveillance and control efforts.
In addition to the large number of foreign herdsmen undertaking transhumance in
northern Togo every dry season, one third of local herds were reported to be seasonally
transhumant. Women were also shown to be a more mobile sub-group of the local
population, and further investigation of the needs of these mobile groups is warranted.
Although the level of satisfaction with the local health centres was generally high, the
cost of services was an exception and may reflect a financial barrier. Increased distance
to the local health centre reduced the utilisation of skilled birth attendants by women,
and may be an important barrier to accessing health care. Livestock herding duties of
Fulani children resulted in poorer school attendance, and the impact on physical,
intellectual and social development should be explored.