Causes of Mortality and Disease in Rabbits and Hares: A Retrospective Study

SIMPLE SUMMARY: Domestic and wild lagomorphs, especially rabbits and hares, are important from an economic, ecological and public health point of view. Both rabbits and hares are susceptible to a wide variety of pathological disorders, so that the knowledge of the different risk factors, causes of death or disease and prevalence rates is relevant from a health, economic and welfare perspective. Despite the accumulation of information on lagomorph medicine and pathology, comprehensive published compilations of diagnostic cases in rabbits and hares are scarce. Between 2000 and 2018, 325 lagomorphs (rabbits and hares) from northern Spain were necropsied. A wide variety of conditions were identified. The health problems most frequently diagnosed were related to parasitic conditions (n = 65; 24.34%), bacterial diseases (n = 56; 20.97%), nutritional and metabolic disorders (n = 48; 17.97%), viral infections (n = 31; 11.61%), miscellaneous causes (n = 31; 11.61%), neoplasms (n = 12; 4.49%), toxicoses (n = 11; 4.11%), trauma-related injuries (n = 9; 3.37%) and finally, congenital diseases (n = 4; 1.49%). The species, sex, age and time of the year were predisposing factors in many of the conditions identified. The frequency of presentation and main pathological findings of these disorders were consistent with the most important lagomorph diseases reported in other European countries and other referenced studies. ABSTRACT: In this study we determined the causes of mortality and disease in a total of 325 lagomorphs (rabbits and hares) in northern Spain between 2000 and 2018. Risk factors such as the species, age, sex, time of year and origin were also considered. Clinical signs, gross and histopathological findings and ancillary test results were the basis for the final diagnoses that were reviewed to classify and identify the different disorders. A total of 26 different conditions were identified. A single cause of death or illness was detected in 267 animals. They were grouped into parasitic conditions (n= 65; 24.34%) represented by encephalitozoonosis, hepatic coccidiosis, hepatoperitoneal cysticercosis, intestinal coccidiosis, parasitic gastritis and cutaneous ectoparasitosis; bacterial diseases (n = 56; 20.97%) including pseudotuberculosis, blue breast, skin abscesses, tularemia, pneumonic pasteurellosis and staphylococcal infections; nutritional and metabolic diseases (n = 48; 17.97%) with epizootic rabbit enteropathy, hepatic steatosis and pregnancy toxemia as prominent diseases; viral infections (n= 31; 11.61%) comprising rabbit hemorrhagic disease and myxomatosis and miscellaneous causes (n = 31; 11.61%) where rabbit enteritis complex, renal conditions (nephrosis), heat stroke, and arterial bone metaplasia were included; neoplasms (n = 12; 4.49%) represented by uterine adenocarcinoma, mammary adenocarcinoma, cutaneous fibroma, intestinal lymphoma and hepatic cholangiocarcinoma; toxicoses (n = 11; 4.11%); trauma-related injuries (n = 9; 3.37%) and finally congenital diseases (n = 4; 1.49%). In 58 animals of the study, some of these conditions were presented jointly. We discuss the detection frequency, possible causes or associated factors of the different pathologies as well as the importance of the different variables considered.