Zoo Felids Research Articles

Continuous Video Monitoring of Zoo Cheetahs (Acinonyx jubatus jubatus) Reveals Differential Engagement Patterns for Environmental Enrichment Items Based on Sensory Category

Strategically enriching the environment of zoo felids to encourage innate behaviors is essential to good welfare. To investigate how engagement differs among sensory-based enrichment, six items representing tactile (firehose log, Jolly Eggs), visual (mirror, movie), and olfactory (cinnamon, cologne) sensory categories were offered to three adult cheetah siblings. Each item was offered four times: twice during daytime hours and twice overnight (≥5 h/occasion). Static video monitoring was used to investigate engagement frequency and duration for each item and to observe grooming behaviors. Cheetahs engaged with visual enrichment more frequently (p < 0.05) and for greater (p < 0.05) periods than other items. Allogrooming occurred most frequently (p < 0.05) when the movie was provisioned at night. Tactile enrichment was only modestly engaged, with fewer but longer engagements (p < 0.05) at nighttime than at daytime. Autogrooming frequency did not vary among enrichment items but was greater (p < 0.05) at night than day. These findings showed that zoo cheetah responses to sensory enrichment items differed based on type and time of day. Visual stimuli were favored, whereas olfactory stimuli were generally ignored. This illustrates the benefit of diverse sensory-specific enrichment strategies. Such dynamic strategies can help overcome the challenge of individual preferences to encourage engagement reflective of the animal’s natural behaviors.

Cross-genera amplification and identification of Colpodella sp. with Cryptosporidium primers in fecal samples of zoo felids from northeast China.

The protozoans include many intracellular human pathogens. Accurate detection of these pathogens is necessary to treat the diseases. In clinical epidemiology, molecular identification of protozoan is considered a more reliable and rapid method for identification than microscopy. Among these protozoans, Cryptosporidium considered being one of the important water-borne zoonotic pathogens and a major cause of a diarrheal disease named cryptosporidiosis in humans, domestic animals, and wild animals. This study was aimed to identify Cryptosporidium in zoo felids (N= 56) belonging to different zoo of China, but accidentlly Colpodella was encountered in the zoo felids sample and phylogenetic data confirmed this unexpected amplification from fecal samples using two-step nested-PCR. Phylogenetic analysis revealed the fact about the specific primers used previously by many researchers and cross-genera amplification. We came to know that genetically sequenced amplicon gives more accurate identification of species. This study suggests more investigation on Colpodella which has been neglected previously but gains the attention of researchers after identified from humans and animals and has been known to correlate with neurological symptoms in patients.

Symmetric Dimethylarginine is a Promising Biomarker for the Early Detection of Age-Related Kidney Dysfunction in Zoo Felids

Abstract Chronic renal failure is one of the leading causes of death in African lions, cheetahs, and tigers. Conventional methods to measure renal dysfunction include measuring serum creatinine and blood urea nitrogen (BUN). Symmetric dimethylarginine (SDMA) measurement is a reliable predictor of renal dysfunction in the domestic cat because SDMA serum levels increase early when the kidneys are damaged. Serum SDMA levels were assessed and correlated with creatinine as well as BUN from healthy captive Bengal tigers and lions at the Everland Zoo in Korea. Serum SDMA concentrations were increasingly associated with increased age in lions. However, SDMA concentrations were higher in some young Bengal tigers than in older ones, which may allow for earlier renal dysfunction detection in these young cats than would be BUN and creatinine alone. In Bengal tigers, the correlation between the SDMA and BUN was slightly higher than that between SDMA and creatinine. In lions, SDMA correlated better with creatinine than with BUN concentration. These results show that serum SDMA concentration can be used as a biomarker for age-associated renal dysfunction. SDMA measurement may be an essential preventive management method in zoos.

Exploration of Zoo felids in North-East China for the prevalence and molecular identification of Cryptosporidium spp.

Cryptosporidium spp. is a protozoan having the potential to cause zoonosis in humans and animals. Despite the zoonotic importance of this protozoan parasite, limited data are available about its prevalence in zoo felids in North-Eastern China. Hence, the current study was designed to determine the occurrence and molecular characterization of Cryptosporidium spp. from the fecal samples of captive zoo felids. Fecal samples (N = 244) were collected from different felids from five different zoos of North-Eastern China. 18S rRNA gene was amplified from the genomic DNA using species specific primers in nested polymerase chain reaction (nPCR) and Cryptosporidium parvum and Cryptosporidium spp. was found. The overall prevalence of Cryptosporidium was 9.43% (23/244). The 18S rRNA gene similarity analysis showed that 6 Cryptosporidium isolates were Cryptosporidium parvum and the remaining 17 Cryptosporidium isolates were resembling to a Cryptosporidium spp., which is similar to Cryptosporidium NEV10. Phylogenetic tree was constructed based on 18S rRNA of Cryptosporidium spp. The similarity of Cryptosporidium parvum was with its other isolates in China, India, Iran, Iraq, Turkey, Czech Republic, Spain and USA while Cryptosporidium NEV10 alike had a close relationship with Turkish isolates. In conclusion, Cryptosporidium was prevailing in feline animals of China zoo and zoo officials are directed to consider their control policy as it can be a cause of zoonosis.

Influence of pork and pork by-products on macronutrient and energy digestibility and palatability in large exotic felids.

Two experiments were conducted to evaluate digestibility and palatability of a new commercial pork-based raw diet for zoo-managed felids. Currently 2 protein sources (beef or horse) comprise the majority of commercial raw meat diet formulations for exotic carnivores in zoological institutions. Pork-based diets have traditionally not been widely utilized and thus nutrient digestibility of pork has not been adequately evaluated in exotic carnivores. The objectives of this study were 1) to determine if a pork-based diet had similar apparent total tract macronutrient digestibility and fecal scores as standard zoo carnivore diets formulated with either horse or beef, in large exotic felids and 2) evaluate palatability of pork for use in zoos. Ten exotic felids were used including cheetahs (; 3), jaguars (; = 3), leopards (; 2), puma (; 1), and Bengal tiger (; 1). Dietary treatments consisted of 4 raw meat diets: 1 horse-based (Horse), 2 beef-based (B1, B2), and 1 pork-based diet (Pork). Fecal scores also were evaluated (1 = hard to 5 = watery/liquid). This randomized crossover design study consisted of 4 periods, each 10 d for treatment adaptation followed by 4 d of sample collection. Dry matter and crude protein apparent digestibility values were greater ( < 0.05) in felids fed Pork (88.0 and 95.7%) compared with felids fed Horse (83.6 and 92.7%) and B2 (85.6 and 93.1%). Apparent organic matter digestibility was greater ( < 0.05) in felids fed Pork (90.8%) than felids fed Horse (88.5%). Apparent fat digestibility values were high across all treatments but were greater ( < 0.05) in felids fed Pork (98.5%) compared with felids fed B1 (95.5%) or B2 (96.5%). Gross energy digestibility values were greater in felids fed Pork (92.4%) compared with B1 (90.2%). Average fecal scores were 2.30, 2.94, 3.42, and 3.54 for Horse, Pork, B1 and B2, respectively; and were different ( < 0.05) between treatments with exception of B1 and B2 that did not differ. Felids approached the pork diet first in 65.6% of observations and tasted the pork diet first in 71.9% of observations, compared with a beef-based raw diet. Based on results, the evaluated pork-based diet had similar apparent total tract macronutrient digestibility and palatability compared with standard zoo carnivore formulations. In conclusion, pork-based diets could be included among dietary options for large zoo felids.

Naturally Occurring and Melengestrol Acetate-associated Reproductive Tract Lesions in Zoo Canids

As husbandry practices have improved, safe and effective contraception for captive wildlife management has become a necessity. Melengestrol acetate (MGA), a synthetic progestin, is highly effective and has been used in many zoo species. Long-term use of MGA has been associated with uterine lesions in zoo felids, but effects in zoo canids have not been evaluated. This retrospective study documented spontaneously occurring lesions and investigated the impact of MGA on the reproductive health of zoo canids. Reproductive tracts from adult females were submitted by US zoos to the Association of Zoos & Aquariums' Wildlife Contraception Center Health Surveillance Program. Reproductive tracts were sampled and processed for histopathologic examination following standard protocols. Microscopic evaluations were performed without prior knowledge of MGA treatment status. Prevalence of uterine lesions was evaluated and compared between MGA-treated animals (n = 20) and control (untreated) animals (n = 61). Common lesions within the study population as a whole included endometrial hyperplasia (predominantly cystic) (53%), hydrometra (33%), and adenomyosis (25%). Treatment with MGA was a risk factor for endometrial hyperplasia, hydrometra, fibrosis, and adenomyosis. Uterine mineralization occurred exclusively in MGA-treated animals. Results indicate that MGA contraception can lead to lesions that may permanently impair the fertility of females. Therefore, if long-term contraception of zoo canids is necessary, the use of alternate methods of reproductive control such as gonadotropin-releasing hormone (GnRH) analogs or GnRH vaccines that reduce gonadal hormone exposure should be pursued.

Neoplasia in Felids at the Knoxville Zoological Gardens, 1979–2003

A review of medical records and necropsy reports from 1979-2003 found 40 neoplasms in 26 zoo felids, including five lions (Panthera leo, two males and three females), three leopards (Panthera pardus, two males and one female), one jaguar (Panthera onca, female), 11 tigers (Panthera tigris, three males and eight females), two snow leopards (Panthera uncia, one male and one female), two cougars (Felis concolor, one male and one female), one bobcat (Felis rufus, male), and one cheetah (Acinonyx jubatus, female). Animals that had not reached 3 yr of age or had been housed in the collection less than 3 yrs were not included in the study. Neoplasia rate at necropsy was 51% (24/47), and overall incidence of felid neoplasia during the study period was 25% (26/103). Neoplasia was identified as the cause of death or reason for euthanasia in 28% (13/47) of those necropsied. Neoplasms were observed in the integumentary-mammary (n=11), endocrine (n=10), reproductive (n=8), hematopoietic-lymphoreticular (n=5), digestive (n=3), and hepatobiliary (n=2) systems. One neoplasm was unclassified by system. Multiple neoplasms were observed in 11 animals. Both benign and malignant neoplasms were observed in all systems except for the hematopoietic-lymphoreticular systems where all processes were malignant. Of the endocrine neoplasms, those involving the thyroid and parathyroid glands predominated (n=8) over other endocrine organs and included adenomas and carcinomas. In the integumentary system, 63% (7/11) of neoplasms involved the mammary gland, with mammary carcinoma representing 83% (6/7) of the neoplasms. The rates of neoplasia at this institution, during the given time period, appears to be greater than rates found in the one other published survey of captive felids.

Seroepidemiology of Toxoplasma gondii in Zoo Animals in Selected Zoos in the Midwestern United States

Toxoplasma gondii infections in zoo animals are of interest because many captive animals die of clinical toxoplasmosis and because of the potential risk of exposure of children and elderly to T. gondii oocysts excreted by cats in the zoos. Seroprevalence of T. gondii antibodies in wild zoo felids, highly susceptible zoo species, and feral cats from 8 zoos of the midwestern United States was determined by using the modified agglutination test (MAT). A titer of 1:25 was considered indicative of T. gondii exposure. Among wild felids, antibodies to T. gondii were found in 6 (27.3%) of 22 cheetahs (Acynonyx jubatus jubatus), 2 of 4 African lynx (Caracal caracal), 1 of 7 clouded leopards (Neofelis nebulosa), 1 of 5 Pallas cats (Otocolobus manul), 12 (54.5%) of 22 African lions (Panthera leo), 1 of 1 jaguar (Panthera onca), 1 of 1 Amur leopard (Panthera pardus orientalis), 1 of 1 Persian leopard (Panthera pardus saxicolor), 5 (27.8%) of 18 Amur tigers (Panthera tigris altaica), 1 of 4 fishing cats (Prionailurus viverrinus), 3 of 6 pumas (Puma concolor), 2 of 2 Texas pumas (Puma concolor stanleyana), and 5 (35.7%) of 14 snow leopards (Uncia uncia). Antibodies were found in 10 of 34 feral domestic cats (Felis domesticus) trapped in 3 zoos. Toxoplasma gondii oocysts were not found in any of the 78 fecal samples from wild and domestic cats. Among the macropods, antibodies were detected in 1 of 3 Dama wallabies (Macropus eugenii), 1 of 1 western grey kangaroo (Macropus fuliginosus), 1 of 2 wallaroos (Macropus robustus), 6 of 8 Bennett's wallabies (Macropus rufogriseus), 21 (61.8%) of 34 red kangaroos (Macropus rufus), and 1 of 1 dusky pademelon (Thylogale brunii). Among prosimians, antibodies were detected in 1 of 3 blue-eyed black lemurs (Eulemur macaco flavifrons), 1 of 21 ring-tailed lemurs (Lemur catta), 2 of 9 red-ruffed lemurs (Varecia variegata rubra), and 2 of 4 black- and white-ruffed lemurs (Varecia variegata variegata). Among the avian species tested, 2 of 3 bald eagles (Haliaeetus leucocephalus) were seropositive. Among 7 possible risk factors, sex, freezing meat temperature (above -13 C vs. below -13 C), washing vegetables thoroughly, frequency of feral cat sightings on zoo grounds (occasionally vs. frequently), frequency of feral cat control programs, capability of feral cats to enter hay/grain barn, and type of animal exhibit, exhibiting animals in open enclosures was the only factor identified as a significant risk (OR 3.22, P = 0.00).

Comparative Pathology of Mammary Gland Cancers in Domestic and Wild Animals

Mammary cancer occurs among all taxonomic groups, and comparing the disease in animals with breast cancer in women could greatly improve our understanding of the relevant risk factors and genetic profiles for this disease. Differences in cancer prevalence between carnivores and herbivores and between captive and wild carnivores are striking and support the hypotheses that diet and reproductive history are major risk factors. Domestic dogs and cats have a high prevalence of mammary tumors, and the majority of tumors in cats are aggressive cancers. Many domestic dogs and cats are prevented from breeding, resulting in their being exposed to recurrent estrogen peaks followed by high persistent levels of progesterone. Therefore progesterone appears to be a significant risk factor for cancer development. Supporting this suspicion is the observation that most mammary cancers in zoo cats are in those treated with the potent synthetic progestin contraceptive, melengestrol acetate. The more common morphologic types of mammary cancer in canids and felids include tubulopapillary, solid, cribriform, comedo and anaplastic carcinomas. Dogs also develop complex carcinomas, which likely evolve from the complex adenomas or mixed tumors that are so common in this species and are promoted by exogenous progesterone treatment. Among zoo felids, jaguars are at higher risk for mammary cancer and also have a high prevalence of ovarian papillarycystadenocarcinomas, a profile similar to women with BRCA1 mutations. As for women, estrogen (ER) and progesterone receptor (PR) expression varies in canine and feline mammary cancers. In general, ER expression is low, but PR expression persists in most cancers. Alterations in molecular controls of cell proliferation or survival in breast cancer, such as cyclin A and p53 expression, have been identified in dog and cat mammary cancers. Overall, spontaneous mammary cancers in cats and dogs make excellent models for human breast cancer, and knowledge of mammary carcinogenesis would be greatly enhanced across all species by a "One Medicine" approach.

Taurine and zoo felids: considerations of dietary and biological tissue concentrations

Taurine (TAU) is an essential amino acid required in the diets of Felidae at concentrations ranging between 0.04 and 0.2% on a dry matter (DM) basis (in purified, highly digestible diets, and canned diets, respectively). Although the domestic cat seems to be an appropriate physiologic model for zoo felids, it is sometimes difficult to assess TAU status in zoo feeding programs owing to scattered information on feed ingredient TAU content as well as a lack of normal ranges for assessment of TAU in biological tissues. Knowing that TAU is required in the formulation of hand-rearing diets for exotic felids, the TAU content of 38 ingredients or products used in zoo carnivore feeding or hand-rearing programs was summarized, including 21 new feedstuffs for which TAU data were previously lacking. The kitten milk replacer contained a lower than expected value for TAU. Commercially prepared frozen or canned meat products, seafood products, whole rodent prey, and most strained meat jarred baby foods contained adequate TAU; chunk meats, and some specific types of jarred baby food meats were considerably lower in TAU content (</=0.10% DM) than other foodstuffs. TAU concentrations in plasma and whole blood of eight spp. of zoo felids sampled opportunistically fell within reference ranges for domestic cats (80-120 and 300-600 nmol/ml in plasma and whole blood, respectively). Plasma concentrations are a useful measure of dietary impact, whereas whole blood concentrations seem to reflect tissue storage of this nutrient. Zoo Biol 26:517-531, 2007. (c) 2007 Wiley-Liss, Inc.

Comparison of several types of enrichment for captive felids

Enrichment can increase the complexity of the captive environment and possibly enhance captive animals' well-being by stimulating active behaviors and reducing stereotypical behaviors commonly seen in zoo felids. In this study, three different enrichment items were added to outdoor enclosures of felids at the Montgomery Zoo to test their effects on activity levels and stereotypic pacing. Bones, frozen fish, and spices (cinnamon, chili powder, and cumin) were presented over a 3-month period to six species of felids: cheetah, cougar, jaguar, lion, ocelot, and tiger. Proportion of time spent engaging in active behaviors and stereotypic pacing were compared before, during, and after treatments. All treatments resulted in a significant increase in activity level from baseline (bones: +15.59%; frozen fish: +35.7%; spices: +12.38%). Effects of enrichment items on activity levels were not sustained 7 days after removal. Proportion of time spent pacing significantly decreased during presentation of spices (-21.25%) and frozen fish (-26.58%), but not with the addition of bones. However, only the effect of frozen fish on stereotypic behavior was sustained 7 days after removal of the enrichment item. In conclusion, bones, spices, and frozen fish are inexpensive and easy-to-administer enrichment items that may be used to increase active behaviors of captive felids. Zoo Biol 26:371-381, 2007. (c) 2007 Wiley-Liss, Inc.

Histologic Features of Mammary Carcinomas in Zoo Felids Treated with Melengestrol Acetate (MGA) Contraceptives

Melengestrol acetate (MGA), a potent synthetic progestin, has been used as a contraceptive in zoo felids since 1975. Mammary gland carcinomas have been linked to MGA treatment in zoo felids, but the histologic features of these tumors and steroid receptor expression have not been described. Zoo felid mammary tumors were requested from participating zoos from 1986 through 1998, and 31 mammary carcinomas from 28 MGA-treated and 3 untreated felids were received. The carcinomas were evaluated on the basis of histologic pattern, tumor grade, and occurrence of metastasis; then features of the tumors were compared to determine if carcinomas in MGA-treated felids differed from those that occur spontaneously. Estrogen- and progesterone-receptor expression was evaluated in 17 of the 31 carcinomas. Of the 31 tumors, 22 (70.9%) had multiple histologic patterns, 29 (93.5%) were high grade, and 28 (90.3%) had metastasized. Within tumors, the tubulopapillary pattern was most common (87.1%, n = 27); solid (61.3%, n = 19), cribriform (38.7%, n = 12), and comedone (25.8%, n = 8) patterns were less common; and the mucinous (3.2%, n = 1) pattern was rare. Both MGA-treated and untreated zoo felids had similar patterns and grades of mammary gland cancer as well as prevalence of metastasis. These results indicate that mammary carcinomas in zoo felids are high grade with a predominant tubulopapillary pattern and aggressive behavior. Five of 17 carcinomas expressed progesterone receptors, and 1 of 17 expressed estrogen receptors. Although more zoo felids with cancer had been exposed to MGA in this study, mammary carcinomas were similar in appearance and behavior in untreated and MGA-treated zoo felids. The association of MGA with the development of malignant mammary gland tumors should be considered when using this contraceptive in zoo felids.

EFFECTS OF PORCINE ZONA PELLUCIDA IMMUNOCONTRACEPTIVES IN ZOO FELIDS

Methods of contraception are necessary for management of zoo felids; however, the most commonly used contraceptive (melengestrol acetate implant) is associated with serious adverse reactions with long-term use. Porcine zona pellucida (pZP) vaccines are promising as contraceptives, but their safety in zoo felids has not been tested. pZP vaccine was administered to 27 female felids representing 10 species, including African lion (Panthera leo), Asian leopard (P. pardus), jaguar (P. onca), tiger (P. tigris), snow leopard (P. uncia), cougar (Felis concolor), Siberian lynx (F. lynx), Canada lynx (F. canadensis), serval (F. serval), and bobcat (F. rufus), in 15 facilities. Over 6 wk, each animal received three i.m. injections of 65 microg pZP with Freund's complete adjuvant (FCA), Freund's incomplete adjuvant, or carbopol as the adjuvant. Behavioral signs of estrus were seen in 14 of the vaccinated felids. An unacceptably high incidence of adverse reactions was seen including injection site swelling, lameness, limb swelling, or abscessation (or all) in five felids after injection with FCA as the initial adjuvant. Adverse behavioral signs, including increased irritability and aggression, were seen in four felids. Six of the felids were assayed for antibodies against pZP during the 12 mo after vaccination; all showed antibody production. Antibody levels appeared to peak 1-4 mo after vaccination began, although elevated antibody levels persisted in two animals for > 12 mo after the first injection. All vaccinated felids were ovariohysterectomized 3-13 mo after vaccination. Folliculogenesis was present in all treated animals, and there was no histopathologic evidence of inflammatory damage to ovaries. Contraceptive efficacy was not specifically evaluated in this study; however, two of the three felids housed with an intact male became pregnant during the study, one of which gave birth to healthy cubs.

Blastomycosis in nondomestic felids.

Blastomycosis was diagnosed in six nondomestic felids from eastern Tennessee, including two Asian lions (Panthera leo persicus), one African lion (Panthera leo), one Siberian tiger (Panthera tigris), one cheetah (Acinonyx jubatus), and one snow leopard (Panthera uncia). Clinical signs included lethargy, anorexia, weight loss, dyspnea, sneezing. ataxia, and paresis. Variable nonspecific changes included leukocytosis, monocytosis, moderate left shift of neutrophils, moderate hypercalcemia, hyperproteinemia, and hyperglobulinemia. Thoracic radiographs revealed interstitial and alveolar changes, consolidation or collapse of a lung lobe, bullae formation, and a pulmonary mass. Agar gel immunodiffusion (AGID) serology for Blastomyces dermatitidis was performed in five felids and was positive in three. The tiger had cerebral blastomycosis and was positive for AGID serologic tests of both cerebrospinal fluid and serum. One percutaneous lung aspirate in the snow leopard and one bronchial aspirate in an Asian lion demonstrated B. dermatitidis organisms. whereas tracheal wash samples and a nasal discharge were nondiagnostic in others. Treatment with itraconazole was attempted in four cats. The tiger improved before euthanasia, whereas the others did not survive beyond initial treatments. In four felids, B. dermatitidis was found in the lungs and tracheobronchial lymph nodes associated with a florid pyogranulomatous reaction; the tiger had a pyogranulomatous encephalomyelitis, and the cheetah had a single pulmonary granuloma. Thoracic radiography, cytologic examination of lung lesion aspirates, and B. dermatitidis AGID serology should be performed on clinically ill zoo felids in endemic areas to rule out blastomycosis.

Endometrial hyperplasia and mineralization in zoo felids treated with melengestrol acetate contraceptives.

Melengestrol acetate (MGA) contraceptives are widely used in zoo felids to regulate fertility and may have deleterious effects on endometrial health. To determine whether MGA exposure was associated with endometrial disease, the genital tracts of 212 zoo felids (99 MGA treated and 113 control) representing 23 species were evaluated. Adenomatous and cystic hyperplasia were prevalent in both MGA-treated (85%) and control (61%) groups, and the risk of developing these lesions increased with age. Treatment with MGA further increased the risk of developing advanced hyperplasia regardless of dose, and treatment for >72 months significantly elevated that risk, whereas parous animals had a lower risk. Endometrial polyps, fibrosis, adenomyosis, and hydrometra occurred in both MGA-treated and control animals. MGA treatment was associated with an increased risk of hydrometra and mineralization but not of adenomyosis, polyps, or fibrosis after adjusting for advanced hyperplasia. Acute or chronic endometritis were associated with advanced hyperplasia but not with MGA treatment. These results indicate that proliferative and inflammatory endometrial lesions are common spontaneous diseases in zoo cats, and MGA contraceptives increase the risk of some diseases. The association of MGA with endometrial lesions that could impair fertility should be considered when using this contraceptive in genetically valuable felids.

Genital tract smooth muscle tumors are common in zoo felids but are not associated with melengestrol acetate contraceptive treatment.

In a survey of gynecologic lesions in female zoo felids conducted to determine if the widely used progestin contraceptive melengestrol acetate (MGA) had adverse effects, numerous leiomyomas and leiomyosarcomas were detected. This current study aimed to characterize the morphologic features of these tumors, determine their prevalence, and assess if MGA was a risk factor for their genesis. Genital tracts from 219 zoo felids representing 23 species were evaluated, and leiomyomas were detected in 24% of the felids. Leiomyomas were often multiple and occurred in the myometrium, ovary, or adjacent broad ligament. The risk of developing leiomyomas increased with age, but MGA treatment or parity had no effect. Five other felids had leiomyosarcomas. Leiomyosarcomas were distinguished from poorly demarcated leiomyomas by the presence of local invasion, metastasis, and cellular atypia, but necrosis and mitotic rate were not distinguishing criteria. Four of five felids with leiomyosarcomas had been treated with MGA. These results indicate that leiomyomas are common spontaneous lesions in the genital tracts of zoo felids and their genesis is not linked to MGA exposure. Whether progression to malignancy is promoted by MGA warrants further investigation.

Efficacy of levonorgestrel when administered as an irradiated, slow‐release injectable matrix for feline contraception

AbstractReliable and safe methods of reversible contraception are needed for use in zoo felids. The efficacy of levonorgestrel (LNG) as a contraceptive, when delivered as a cesium‐irradiated, slow‐release, injectable matrix, was tested in domestic cats as a model for exotic cats. An increase (P = 0.0017) in body weight was observed in treated but not control queens (P = 0.2146). All control queens (n = 6), which received injections of matrix only, but none of the LNG‐treated queens (n = 6) became pregnant during the trial. Levonorgestrel was effective in preventing pregnancy for at least 36 weeks after two injections of drug‐loaded formulations (40 mg/kg body weight), administered 68 days apart. Throughout the study, all control queens displayed luteal activity and fluctuating fecal estradiol concentrations, whereas the LNG‐treated queens displayed lower estradiol concentrations and no luteal activity after treatment. We conclude that LNG, when delivered as a cesium‐irradiated, slow‐release, injectable matrix, is an effective contraceptive in domestic cats, reducing follicular activity, and thus, preventing mating and luteal activity. Zoo Biol 20:407–421, 2001. © 2001 Wiley‐Liss, Inc.