Abstract
Caseous lymphadenitis (CLA) is a bacterial disease of small ruminants causing abscesses in lymph nodes of the body and internal organs. A longitudinal study from 2011 to 2019 was undertaken at Ataye site of Debre Birhan Research Center to estimate the prevalence and incidence, identify associated risk factors, and characterize the causative bacteria. 1025 goats were followed up for the CLA study. Survival analysis was done using SAS 9.4 software program. Biochemical tests and Biolog microbial identification system were used to characterize the bacteria. In the recurrent survival data analysis, there were 1,138 clinical observations and 214 CLA cases (18.8% prevalence) based on clinical diagnosis. The incidence rate was 0.14 cases per animal year. From a total of 214 cases, 130 have occurred once and 84 cases are recurrent cases following first cases. The cumulative failure rates were 68% for newborn and 64% for yearling age groups. The parotid lymph node was the most frequently affected site. Proportional hazard analysis results showed that sex, age, and breed were associated (p < 0.05) with CLA incidence. Females, newborn age group, Boer, and Boer × Central Highland Goat (CHG) were at higher risks compared to males, yearling age group, and CHG goats, respectively. The present study indicated that a high incidence rate of CLA in the goat farm is difficult to control and prevent because of its poor response to clinical treatment. Thus, control and prevention should focus on the spread of the disease such as isolation of clinically sick animals, culling, and vaccination of flocks.
Highlights
Abscess disease, commonly known as Morel’s disease and caseous lymphadenitis (CLA), is a bacterial disease of sheep and goat causing abscesses in lymph nodes of the body and internal organs, especially the lung
Study Area and Animals. e study was conducted at the on-station Boer × Central Highland Goat cross-breeding program carried out at Ataye Research site, Debre Birhan Agricultural Research Center, Ethiopia. e site is located in central Ethiopia and the climate is characterized by bimodal rainfall consisting of the long rainy season (June-September), short rainy season (February-May), and dry season (October-January) [13]. e site’s geographic coordinate reference is 10°35′ N latitude and 39°93′ E longitude and is located at 1491 m above sea level altitude (Figure 1)
Pus samples from 32 goats with lesions suspected of caseous lymphadenitis were taken after shaved and disinfected with 70% alcohol or savlon, and an incision was made with a sterile blade and the samples were transported in icebox to the microbiology laboratory of Debre Birhan Agricultural Research Center
Summary
Commonly known as Morel’s disease and caseous lymphadenitis (CLA), is a bacterial disease of sheep and goat causing abscesses in lymph nodes of the body and internal organs, especially the lung. It is a contagious disease distributed worldwide and lacks effective control measures. CLA is a disease caused by Corynebacterium pseudotuberculosis bacteria. It is commonly found in animals, such as sheep, goat, and cattle, from where the infection is transmitted to humans. Accurate CLA diagnosis is based primarily on clinical observations (external abscesses) [5] and the identification of C. pseudotuberculosis by phenotypic and biochemical tests; this is important to differentiate this bacterium from other abscess inducing pathogenic agents, such as Arcanobacterium pyogenes or Pasteurella multocida [2, 6, 7]
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