Warning: This blog contains veterinary images that some may consider graphic and inappropriate for our younger blog readers.
We have a guest blogger this week, Dr. Kadie Anderson, DVM at Point Defiance Zoo & Aquarium!
The Red Wolf Species Survival Plan currently manages 199 wolves, of which 59 are housed at Point Defiance Zoo & Aquarium (PDZA) red wolf facilities. In the summer of 2011, staff veterinarians at PDZA noticed an increase in the number of middle aged to older female wolves developing severe uterine infections (e.g. pyometra). In many instances, wolves diagnosed with these infections had to be spayed. This action removes the animal from contributing genetically to the population and can complicate the management of a critically endangered species such as the red wolf. Managers of small, genetically restricted populations often select older individuals for breeding purposes to maximize their genetic contribution to the population. As middle aged to older animals are predisposed to the development of pyometra (and yet are often selected for breeding), further investigation was needed to better understand this condition in red wolves.
Female red wolf “Millie” at PDZA with a litter of pups in 2012.
Veterinarians are well informed about how pyometra develops in the domestic dog but are still working to understand how the process differs in non-domestic species such as the red wolf. In the domestic dog, pyometra is often accompanied by cystic endometrial hyperplasia (CEH). This describes changes in the uterus which causes a cystic and thickened uterine lining and predisposes the uterine environment to bacterial infection and pyometra at certain stages of the reproductive cycle. In the domestic dog, hormones, reproductive history (e.g. litters produced), and age are all believed to contribute to the development of this syndrome. Shortly after PDZA identified pyometra as an issue in red wolves, an assessment by the AZA Canid Taxon Advisory Group supported PDZA’s clinical findings, showing that of the canid species examined, red wolves showed an increased prevalence of CEH and pyometra.
Veterinarian Dr. Nordberg-Wilke ultrasounds a red wolf while PDZA keeper Alicia Pike assists.
Ultrasonographic appearance of an infected uterus.
In our study, 13 adult female red wolves housed at PDZA (ranging in age from 5-10 years) were evaluated for reproductive disease by using ultrasound examination and serum hormone analysis. PDZA partnered with veterinary ultrasonographer Dr. Cindy Nordberg-Wilke to evaluate 13 wolves in December 2011 with 7 of these wolves receiving a follow-up examination in July 2012 for presence or absence of reproductive disease. As hormonal influence has a known role in the development of this disease in domestic dogs, hormone levels were also evaluated and compared against expected ranges.
A normal uterine horn with a grossly distended and infected uterine horn on
the right side of the image and a cystic and enlarged ovary on the right.
A fairly normal red wolf uterus is seen on the right for comparison.
The results of this research project are currently being summarized for publication, but it is expected that the findings in this study will help guide veterinarians toward earlier diagnosis of reproductive disease in red wolves and perhaps improve disease outcome (e.g. females still capable of reproducing). This research has also led to discussion about improving management options in the SSP population for reproductive success and has led to recommendations on how to manage and evaluate at risk females for disease.