Discussion
The present study revealed that FMD is a significant disease in the
study districts with a seroprevalence of 19.8% (n= 76/384). The current
study finding indicated that the overall seroprevalence of FMDV at
individual animal level was 19.8% in the study areas, which is in close
agreement with the previous seroprevalence records of 21% in the Borana
pastoral area (Rufael et al ., 2008), 21% in Borana zone and Guji
zone (OIE & FAO, 2013), 21% in kellema Wollega Zone (Fanta et
at ., 2014), 21 % in Borna pastoral area (Tesfaye, 2006). In contrast
to the current study finding, lower seroprevalence of FMD was previously
reported as mentioned below; 13% in selected districts of western
Ethiopia (Tolosa et al ., 2015), 10.88% in selected district of
eastern showa zone, Oromia regional state (Dinaol et al ., 2016),
12.05% in the Bench Maji zone, Southern Ethiopia (Gelaye et al .,
2009), 8.8% in South Omo Zone (Molla et al ., 2010), 9.5% from
indigenous cattle in southern Ethiopia (Megersa et al ., 2009),
5.53% on quarantined bulls for export at Nazareth and Dire Dawa
stations (Bedru, 2006) and 4.8% in selected districts of western,
Oromia (Milkessa et al ., 2016). These relative lower
seroprevalence of FMD in comparison to the current study might
attributed to diagnostic tests employed, the sampling method, study
population and sites, the geographic structure and timing of infection,
the pastoral production system, which is characterized by a high level
of herd mobility in search of pasture and water, intermingling of
animals at watering points, large herd sizes and frequent contact with
the livestock of neighboring countries through cross-border contact as
well as contact of livestock with FMD virus reservoirs’ of wildlife such
as buffalo, wild pigs, kudu and warthog and other factors (Gelayeet al ., 2009; Megersa et al ., 2009). On the other hand,
relatively higher seroprevalence was previously reported in comparison
to our study from Borna pastoral and agro-pastoral area with 23%
(Berecha et al ., 2011), in Borena and Guji Zones with 24.6 %
(Mekonnen et al., 2011), in west Shewa zone, North Shewa zone and
Addis Ababa with 30.8% (Beksisa, 2017), 32.7% in Guji zone of Oromia
region and 30 % in Yeka district of the city of Addis Ababa as well as
eastern zone of Tigray with 41.5% (Ayelet et al., 2012) and
28.3% seropositivity in Akaki-kality sub-city (Nigussie et al .,
2011). A study finding from neighboring Sudan also revealed that
following an active occurrence of the disease, the seroprevalence of FMD
was reported with 79% in cattle (OIE, 2012). Moreover, according to
Hafez et al . (2014), FMD seropositivity was reported in Saudi
Arabia with 53% seroprevalence and Namatovu et al. ( 2015) as
well reported 77% in infected cattle in Uganda. This seropositivity
variation could be resulted from differences in individual animal breed,
immune status, interaction of cattle with other animals and production
system as well as differences in geographical area or the way sampling
was conducted based on the existence of recent outbreak cases, sample
size, methodology, regular contact with ungulate wildlife (Gelayeet al ., 2009).
The overall herd level seroprevalence in this study was 56.9%
(N=41/72). This finding was in line with the findings of Tesfaye (2006),
who reported the seroprevalence rate of 59 % in Borna pastoral area,
Berecha et al ., (2011), who reported 58.6% in Borna pastoral and
agro pastoral area. The highest herd level seroprevalence (85%)
recorded in Dubti as compared to Asayita (48.13%) and Chifra (44%);
this might be due to the fact that, Dubti is centers for cattle markets
and have high population of small ruminant. This suggests that small
ruminants have an important role in the epidemiology of FMD as they can
serve as potential carriers and transmitters of the disease (Jenbereet al ., 2011) and (Mohamud et al ., 2011).
Among the risk factors considered in the current study age, herd size,
district and contact with ungulate wild life were found to be
statistically significant (P<0.05) in multivariate logistic
regression. In this study, the prevalence of FMD in adult age group was
higher than in young group and this age specific seropositivitity of FMD
was statistically non-significant. Thus, Adult cattle were 2.97 times
more likely to have a chance of contracting FMD than young cattle. This
statistically significant higher seroprevalence of FMDV in old and adult
animals than young cattle in this current study finding was in
accordance with earlier studies of Tolosa et al . (2015) who
reported that adult cattle were 2.7 times more likely to have the chance
of develop disease than young cattle in western Ethiopia, Berechaet al . (2011) in Borna pastoral and agro-pastoral area, Mollaet al . (2010) in south Omo zone and Megersa et al. ( 2009)
in Gamogofa and Sidama zones, Chepkwony et al . (2012) in Awbere
and Babille districts of Jijiga zone. Age association with FMD
seroprevalence was also in close agreement with the previous study of
(Olabode et al ., 2013). The possible justification for age
association with FMD seroprevalence could be due to adult cattle have
acquired the infection through frequent exposure over time to multiple
serotypes of the virus and could get access to mix with other herds at
communal pasture land and market places. Furthermore, it might be due to
persistence of antibodies against FMDV for extended periods of time
(Sangare, 2005). Relatively low seroprevalence in animal groups below 2
years old might be indicative of the existence of passive maternal
immunity and low frequency of exposure (Jenbere et al ., 2011;
Mohamoud et al ., 2011). In our study areas, young animals were
often managed separately at around homestead so that young’s have low
frequency of exposure to the virus and they could also prevailing
passive maternal immunity can give them protection against the disease.
On the contrary, our study result contradicted with Esayas et al .
(2009) and Gelaye et al . (2009), who documented no significant
association between seropositivity of FMD and age of cattle in Bench
Maji zone of southern Ethiopia.
In the current study, seroprevalence of FMD was also significantly
influenced by herd size, which means seroprevalence of antibodies
against FMDV increased with increasing herd size. In our study result,
those animals from medium herd size and large herd size were 2.49 and
6.05 times more likely to develop the disease as compared to those
animals from small herd size respectively by keeping the other factors
constant. Our research finding was in agreement with Tolosa et
al . (2015), Gelaye et al. (2009), Bayissa et al . (2011),
Berecha et al . (2011), who reported that they have positive
relationship between FMD seroprevalence and herd size. This direct
association might be an indication of contagious nature of the disease
and mode of transmission, which is attributed to crowding of animals
that can facilitate frequency of direct contact and hence enhances
chances of transmission.
In our study finding, statistically significant association was found
between study districts and FMD seroprevalence of 35.05% (n=34/97),
14.29% (n=20/140) and 14.97% (n=22/147) in Dubti, Chifra and Asayita
district respectively. Thus, cattle found in Dubti district were 2.49
times more likely to develop the disease as compared with those cattle
found in Asayita district. Our study finding is in close agreement with
previous reports of Milkessa et al . (2016), who reports the
significant variation of Horro (8.2%) and Gobu-sayo (0.8%) districts
of western Oromia regional state and Molla et al . (2010). This
might be due to differences in the movement and distribution of
livestock, the level of contact between herds and ungulate wildlife and
the grazing type in each administrative structure. (Ekboir, 1999) also
suggested that movements of infected animals are by far the most
important dissemination and transmission means for FMDV. Again Paulet al . (1996) in northern Thiland and Bronsvoort et al .
(2004) in Cameroon observed the influence of cattle movement and keeping
animals at homestead in the incidence of FMD.
Cattle that contact regularly with ungulate wild life were 8.97 times
more likely to develop the disease as compared to cattle having no
contact with wild life by keeping other factors constant. This study
finding was in agreement with previous studies of Tolosa et al .
(2015) in western Ethiopia and Molla et al . (2010) in South Omo
zone who reported that cattle that regularly contact with ungulate
wildlife were 3.3 times more likely to develop the disease than cattle
having no contact with wild life. According to Bronvoort et al .
(2008) contact between ungulate wildlife and livestock at watering
points and grazing areas is the main risk factor for FMDV circulation
and it is a challenge for disease control in East Africa (Lazarus,
2012). Although Statistical analysis using the chi-square test and
uni-variable logistic regression showed that contact with animals from
different peasant association/herds appeared to have a significant
effect on seropositivity, multivariable logistic regression showed that
contact animals to other herds/peasant association had no statistically
significant relationship with the seropositivity of the animals
(p>0.05). It was a confounding factor in the relationship
between seropositivity and contact with herds/PAs. However, this result
contradict with Tolosa et al . (2015), who reported the herds were
3.4 times more likely to be seropositive for FMD than herds that did not
have a history of contact with other herds. The difference from the
present study might be because of unequal involvement of differently
contact animal groups in our sampling where majority of our study
animals were animals that regularly contact with other herds/PAs due to
accessibility.