The records of the Zoo/Exotic Pathology Service were studied and the most common types of lesions, causes of lesions/disease, and organs involved from rattlesnake submissions were characterized. Lesions or disease caused by bacteria was the most common single etiologic diagnosis.
A number of papers on disease condition of rattlesnakes are in the literature, but few are more than single case reports. In one survey of reptile diseases,2 rattlesnakes were one of the four most frequently affected species. No indication was given of the percentage of rattlesnakes affected as compared to the percentage in the population.
The records of the Zoo/Exotic Pathology Service were examined to characterize the types of lesions submitted from animals classified in the Crotalinae subfamily (rattlesnakes of both genus Crotalus and Sistrurus). These animals comprise 15.3% of snake submissions (225 of 1475 snakes). This paper presents the etiologies (if determined), morphologic diagnoses, and organs involvement for the species submitted.
Results and Discussion
Twenty-two different types of rattlesnakes were identified, and there was also a group only identified as ‘rattlesnake’ (15.5%). The most common type was the Mohave rattlesnake (65.5%). The four other most common species were the Aruba (3.1%), Black tail and Diamondback (2.2% each), and Massasauga (2.7%).
Lesions/disease caused by bacteria was the most common single etiologic diagnosis (37.5%). In most cases this was a morphologic diagnosis, and follow-up or additional information from the contributor as to culture results was usually not available. Bacterial disease may be more common in rattlesnakes than in the general snake population. The percent of bacterial diseases diagnosed in all snakes in our database was 25.3%. Bacterial osteomyelitis is reported in a variety of snakes; however, our data indicate that it may be more common in rattlesnakes. A previous study identified osteomyelitis in ridgenose (Willards) rattlesnakes (Crotalus willardi) associated with Salmonella enterica SS arizonae.3
Other common etiologies were undetermined (21.9%), neoplastic (12.5%), and parasitic/protozoal and nutritional/metabolic (6.3% each). Neoplasia in rattlesnakes has an incidence that is essentially the same as the incidence of neoplasia in all snakes overall (12.9%). A variety of neoplasms were seen, with no particular tumor being more common.
The most common morphologic diagnoses were hepatitis (10.2%), glomerulonephritis (4.0%), hepatic atrophy (3.1%), and osteomyelitis (2.2%). Hepatitis was most commonly due to bacteria and was often associated with lesions in other organs. Although exact organism(s) were not identified in this review, an infection rate of 37% of snakes has been associated with Salmonella spp. causing lesions in the liver and other internal organs.1
Hepatic atrophy may not be a legitimate diagnosis, but only a reflection of the time since the animal’s last meal. The glomerulonephritis seen was most commonly membranous or membranoprolilferative and the cause usually was not determined. Since approximately 80.0% of diagnoses were other than the four most common, it is obvious that a wide variety of morphologic lesions occur in rattlesnakes.
Organs/organ systems most commonly affected were the liver (33.6%), kidney (19.1%), gastrointestinal tract (8.4%), heart and ovary (4.9% each), bone (4.4%), and lung (3.6%). The incidence of liver and bone involvement was due primarily to the high incidence of bacterial infection in these organs.
1. Cambre RC, Greene DE, Smith EE, Montali RK, Busch M. Salmonellosis and arizonosis in the reptile collection at the National Zoological Park. J Am Vet Med Assoc. 1980;177:800–803.
2. Kaneene JB, Taylor RF, Sikarskie JG, Meyer TJ, Richter A. Disease patterns in the Detroit zoo: A study of reptilian and amphibian populations from 1973 through 1983. J Am Vet Med Assoc. 1985;187:1132–1133.
3. Ramsay EC, Daniel GB, Tyron BW, Merryman JI, Morris PJ, Bemis DA. Osteomyelitis associated with Salmonella enterica SS arizonae in a colony of ridgenose rattlesnakes (Crotalus willardi). J Zoo Wildl Med. 2002;33:301–310.