Rates and causes of mortality in adult dogs in an owned, free-roaming population

Abstract

Introduction: It was estimated that yearly around 23,000 people die of rabies, inflicted by dog bites, in Africa. More than 95% of human rabies cases are caused by dog bites. Rabies is still a public health and economic burden. Vaccination campaigns in canine populations are very important in controlling rabies. To start a successful vaccination campaign, demographic information of the canine population is necessary. Mortality rates are a very important part of this demographic information. To decrease mortality rates, knowledge of the cause of death is also necessary. To obtain more information about the mortality rates and causes in Hluvukani, South Africa a retrospective study Hluvukani (RSH) and longitudinal study Hluvukani (LSH) was started. Hypotheses: Based on other studies, the mortality rate per month is expected to be around 3%. No difference is expected between the mortality rate per month in the RSH and LSH. It is assumed there is a relationship between mortality rates and sexes. Females have a higher mortality rates due to pregnancies and post partum mortality. Higher mortality rates are expected to be found in dogs with an age of five years or more. The most common cause of death in Hluvukani is thought to be diseases (unspecified which diseases exactly) or trauma (accidents, hit by car). Methods & Results: A retrospective study obtained information over a period of 5 months through a questionnaire (n=509). After the retrospective study a longitudinal study was started. Enrolled dogs were visited every two weeks for about two months (n=368). Deaths were reported to the researchers during a revisit or by a phone call. Mortality rate for the retrospective study was 17.9% (3.6% per month) and 1.8% for the longitudinal study (0.9% per month). These mortality rates differ significantly. There was no relationship found between sexes and mortality rates. The mortality rate per age group (1-2, 3-4 or ≥5) did not differ. Most common cause of death in the longitudinal study was trauma (3/6). Causes of death were obtained by a questionnaire, because post mortem examination was not possible. Furthermore, the database of the Hluvukani Animal Clinic database was searched for mortalities (January 2012-May 2014). This study showed rabies (7/10) as the most common cause of death. Both conclusions on causes of death were based on low amount of data, causing these to be less reliable. It is likely that data obtained in the future will increase the reliability of this parameter. Conclusion: To make sure these results are reliable a long-term longitudinal study is needed. This is currently being realized in Hluvukani, South Africa. To determine the cause of death, with more precision, post mortem examination is necessary. Results of this study do contribute to obtain further knowledge of the demography of the canine population in Hluvukani. Hopefully eventually leading to an effective vaccination campaign against rabies in the future.