Assesment of Methods for the Diagnosis of Malignant Catarrhal Fever (Mcf) and Knowledge, Attitudes and Practices Regarding Mcf at Kapiti Plains Ranch

Abstract

Malignant catarrhal fever (MCF) is a sporadic but severe viral disease that affects cattle and is transmitted from wildebeest calves following the wildebeest calving period. Up to now, an effective vaccine or treatment for this disease does not exist hence infected cattle often die causing huge economic losses to both small scale and large scale cattle farmers. The disease has also been associated with human wildlife conflicts and environmental degradation. To date there has been no diagnostics based research nor qualitative assessment of the disease conducted at the Kapiti Plains Ranch Limited, Kenya. This study was therefore aimed to assess the methods for diagnosis and knowledge, attitudes and practises (KAP) of MCF on this ranch. Archived samples (n=123) of clinically confirmed cases of wildebeest associated malignant catarrhal fever (WA-MCF) collected from 2014 to 2016 were tested by nested polymerase chain reaction (PCR) and indirect enzyme linked immunorsorbent assay (ELISA) to evaluate the performance in confirming the clinical cases in the laboratory. Evaluation of the performance of the tests was done in three ways. First, the sensitivity (Se) and specificity (Sp) of indirect ELISA was calculated using nested PCR as a gold standard. Second, the level of agreement between the two tests was assessed by the Cohen’s kappa statistic. Third, the Bayesian agreement index (B.A.I) tested the agreement between these tests in the absence of a gold standard. A KAP study using semi-structured questionnaires (SSQs) with a mix of closed and open ended questions were issued to 60 staff of the ranch to identify various perceptions of WA-MCF in terms of recognition, clinical signs, seasonality of the disease and action taken during the manifestation of the disease. Also, a comparative approach of WAMCF to Contagious Bovine Pleuropneumonia (CBPP), East Coast Fever (ECF), Foot and Mouth Disease (FMD) and Lumpy Skin Disease (LSD) using proportional piling was used to investigate the perception of mortality, annual cases and costs of WA-MCF to these diseases.

In addition the KAP study also sought the ways of controlling WA-MCF from the respondents at the ranch. Of the 123 clinical samples, 62.6% (77/123) were positive by indirect ELISA while 94.3% (116/123) samples were positive by nested PCR. The sensitivity and specificity of the ELISA using nested PCR as a gold standard were 63.8% (95% C.I. 55 -72%) and 57.1% (95% C.I. 25 -85%) respectively. The kappa statistic revealed a value of 0.05 between these tests while the B.A.I. agreement for these assays was better in the positive than in the negative direction with B.A.I. of 76.7% (95% B.C.I. 70-83%) in the positive direction and 15.1% (95% B.C.I. 4-31%) in the negative direction. The KAP study revealed diverse views towards WA-MCF in terms of recognition, clinical signs, seasonality of the disease and action taken during the manifestation of the disease. The disease was revealed to be a very important disease with respect to cattle mortality while being the least important disease with respect to the number of annual cases as the respondents farms are away from wildebeest grazing areas and also in terms of management costs as it lacks an effective vaccine and treatment. A range of methods were suggested for controlling WA-MCF in the case that it could occur in the individual farm of the respondents with the most common being to chase the wildebeest away. The results of this study suggest that when laboratory diagnosis of WA-MCF is needed, nested PCR performs better in confirming the clinical cases of WA-MCF than indirect ELISA. However the logistics of nested PCR make it an unsuitable tool for diagnosing WAMCF as it is expensive, needs well trained personnel and specialized equipment. Future research on WA-MCF should focus on the development of cheap penside techniques for rapid diagnosis during outbreaks. The KAP study demonstrated that most respondents were able to recognize WA-MCF, which will assist in the management of the disease as they can report earlier and take action during outbreaks.

Kapiti Plains Ranch experiences considerable economic losses from WA-MCF, which requires a long-term solution for the wildebeest and cattle to coexist on this ranch. Development of a vaccine would be a long term solution as this will reduce cattle deaths and ensure coexistence between the wildebeests and cattle hence reducing human wildlife conflicts. Further work should be conducted in high risk areas to get a better insight of impacts of the disease. This will enable livestock researchers to collaborate with the cattle owners to give them updated information on new control methods for the disease.