It was observed that the prevalence of seropositive goats increases with age which was also observed by the community (and recorded in the questionnaire). This finding of the study is contradictory to Gizawu et al. (2009), but in agreement with the report of Mamo (1993), who observed the presence of significant variation between age groups.

Moreover, adults also tend to be infected repeatedly since they are exposed and stayed longer in a flock than both young goats and kids. Therefore, the probability to be seropositive at older ages for CCPP  would  be  higher

as compared to kids and young goats.

In addition, the relatively low seroprevalence of CCPP may be related to the ability of the test to detect antibodies that appear first and span for a short duration in the blood. IgM is the first to appear and has little specificity which giving risk to pronounced cross-reactions, and remains in the blood for short duration, while IgG is produced lately and lasts much longer than IgM antibody isotypes (Staak et al., 2001). The CFT has clear limitations: March et al. (2000) observed that 80 to 100% of animals experimentally infected with Mccp in their acute phase were not detected. Based on this report seropositives detected by CF test indicated that there were recent infections and circulation of the causative agent within the flocks.

Flock level seroprevalence

The overall flock level seroprevalence of CCPP was 54.3% in this study implying the presence of the disease in the majority of the flocks in the study area. This result agrees with the result of Mekuria and Asmare (2009) who reported an overall flock level seroprevalence of 54.8%. Difference in seroprevalence at flock level between the agropastoral and sedentary production system were observed in the present study. Flock seroprevalence in the agropastoral area was 61.6% as compared to 35% in the sedentary area. The range of seroprevalences of 0 to 100% between flocks which could be attributed to the differences in husbandry practices in the different districts and production systems. Also there could be differences among herders themselves to react and take measures against the occurrence of diseases within their flocks.

Slightly higher individual seroprevalence differences were seen in the agropastoral areas Itang and Lare (19.2%) when compared to 14.7% in the sedentary area Gambella Zuria. However, nearly twice the number of flocks in the agropastoral areas (61.6%) showed at least one serological reactor for CCPP when compared to the sedentary areas (35%).

The difference in seroprevalences in the various flock size categories was not statistically significant (p>0.05). The finding of this study contradicts with the works of Bekele et al. (2011); flock sizes found in the present study area were relatively small, with an average flock size of 11 to 12 goats (Farm Africa, 1996), as compared to flock sizes found by Bekele et al. (2011), who considered a large flock as a flock having greater than 160 goats per household in the study conducted in Borena and Gujji areas. The flock size variation between the two study areas might be due to different animal husbandry practices and purpose of production.

Risk factors

In the Districts where the production system is agropastoral, especially in Itang and Lare, most of the communities living around the river banks move to dry areas from August to December due to flooding. In this period of time animals congregate in certain areas coming from different localities, thus, favoring the transmission of CCPP from a sick or carrier animal to a healthy animals. Furthermore, during transportation and at temporary waiting pens, goats are kept in close proximity to each other resulting in increased contact rates between animals and, thus enhancing transmission (Lefevre et al., 1987; Crespo, 1994). CCPP transmission by direct contact (by aerogenic route, through droplets released during coughing) is common and a very short period of contact is sufficient to transmit the disease but intimate contact is needed (Thiaucourt and Bolske, 1996). Therefore, a high stocking density in grazing areas in agropastoral production systems (McDermott and Arimi, 2002; Mekasha, 2007) as well as overcrowding and confinement proved to favour circulation of the agent (Lefevre et al., 1987) and thus contributed to the relatively higher CCPP infection as serologically determined by CFT in the agropastoral production system athough the finding is not statistically significant (p>0.05). Therefore, one could conclude that CCPP seems to be equally important in both production systems. However, in the period from August to September animals encounter highly stressing conditions and are more likely exposed to diseases like CCPP, pasteurellosis and endoparasites, as carrier animals may shed more organisms (Thiaucourt and Bolske, 1996).

Sex of the animal was associated with seropositivity in the univariate analysis of risk factors. However, the seroprevalence difference between male and female goats is not biologically plausible but rather due to higher number of female goats in the flocks included in the study area and also most of the females being adults. Thus, the chances of sampling a female and adult goat were quite high. However, the difference due to sex was not statistically significant in the multivariate logistic regression analysis, which is in agreement with the report of Zenebe (2004) and Mekuria and Asmare (2009).

The questionnaire survey and the serological test results indicated the occurrence of Mccp antibodies in all age groups. In both the univariate and multivariate logistic regression analyses the seroprevalence of adult goats was statistically significant different from the seroprevalence in kids. Goats of adult age were 1.84 times more likely to be seropositive than kids. This higher risk could be explained by the fact that the older animals get longer exposure in infected areas and, thus a greater likelihood of infection with the causative agent of CCPP. This finding is in agreement with Mekuria and Asmare (2009) and Bekele et al. (2011) but contrary to Nigatu (2003) and Eshetu et al. (2007) where age was said to play no role in the CCPP epidemiology.

Statistically significant difference in seroprevalence among locations was recorded in the present study. This is in agreement with the report of Mamo (1993); Mekuria and Asmare (2009); and Nigatu (2003). The observed difference might not be accounted due to the difference in agro-ecology for all study areas are in the lowland agroecology; but rather is attributed to the differences in level of accessibility to veterinary services, other infrastructure (road) and the animal husbandry practices. Also from our observation and personal communication to local experts, PA’s that had higher seroprevalence such as Opagna, Badyel, Bonga and Meding Zuria are within a range of 15 to 40 kms distance and thus far from the respective district capital where the animal health service delivery center is located. In addition, from the questionnaire survey we know that in Opagna, Badyel, Bonga and Meding Zuria PA’s most of the respondents used the communal animal management system, significant proportions of the respondents treated their goats by themselves and even some used traditional medicine to treat their goats. All the above conditions and traditional practices that are found in the respective PA significantly contributed to the higher seroprevalence in that particular PA. In addition, the higher prevalence in some PA’s could be attributed to the presence of endemic foci in this area; the odds for seropositivity of goats in Opagna PA were 6.4 times greater than for goats in Zero-1 PA.

The questionnaire survey findings from pastoralist/farmers and from district animal health professionals revealed that CCPP, internal parasitic diseases and contagious ecthyma (Orf) were ranked first, second and third problems, respectively. In South Omo and Arbaminch areas Mekuria and Asmare (2009) also reported CCPP as the first priority disease.

Among the contributing factors for the presence and transmissions of CCPP infection, wet-season, grazing areas and watering points were identified as the major contributors followed by large flock size, introduction of diseased and purchased goats as also reported by other authors (Thiaucourt and Bolske, 1996; Nicholas, 2002). This may be explained by the fact that a new CCPP infection needs proximity to an infected goat (acutely or chronically), latent carriers such as goats which recovered from infection without becoming bacteriologically sterile, and are considered to be responsible for the perpetuation of the disease in a flock. An increasing number of susceptible animals within the population also contributes much to CCPP transmission. The aggregation of goat flocks during watering, grazing and resting times will favor the spread of infection within the flock. In extensive husbandry systems, communal grazing areas and watering points are known to be the major sites for disease transmission (Seifert, 1996).

Community knowledge and perceptions about CCPP, with the local name Zom and its signs described were highly related with those indicated in text book such as coughing, weight loss, sudden death and high mortality (Nicholas, 2002; Bereket, 1995).