Abstract
Zoological institutions and private facilities have become increasingly proactive in the management of cheetahs (Acinonyx jubatus) and helping establish conditions necessary for successful reproduction in captivity. Although the number of facilities breeding cheetahs has recently increased, only 10% of them reported successful reproduction.7 The mortality rates of cheetahs has increased gradually over the last 40 yr. The predominant causes of death in animals over 6 mo of age (n=1266) include kidney and/or liver diseases (21%).8,9 High mortality rates coupled with low reproductive success have left a captive population which is not self-sustaining. The development of reliable methods for health monitoring and reproductive assessment is needed to optimize breeding management of captive cheetahs. This type of program could also assist in managing and conserving the other 36 extant wild felid species maintained in zoos.6
There is relatively little information on ultrasonography in cheetahs.10 Although ultrasonography has been described as a diagnostic and research tool in zoological medicine,5 laparoscopy is still the most common technique for visualizing the internal genital organs. This is particularly true for evaluation of the ovaries and nonpregnant uterus in felids.1 However, ultrasonography could be very useful for non-surgical monitoring of the reproductive status in cheetahs. Furthermore, sonographic examination of the major abdominal organs (such as liver, spleen, adrenals, and kidneys) may provide additional information to determine the relative fitness and breeding potential of individuals.
To develop an ultrasonographic examination protocol, seven captive cheetahs (Acinonyx jubatus; three males and four females) were anesthetized and imaged using transrectal and transcutaneous ultrasonography. Two females and one male were examined four times, before and after hormonal treatment for artificial insemination and electroejaculation, respectively. A portable real-time, B-mode computer sonograph (EUB 405, Hitachi) equipped with a small curved, 7.5 MHz and a 10.0 MHz linear array as well as a 3.5 MHz convex transducer was used for the study. For transrectal application the small 7.5 MHz probe was fitted into an extension specially designed for medium sized mammals which has been applied in several exotic species.2-5
In general, transcutaneous ultrasonography allowed successful imaging of the major abdominal organs, such as liver, spleen, kidney, and urinary bladder. In contrast to transcutaneous ultrasound, transrectal ultrasonography allowed excellent visualization of the entire urogenital tract including vagina, cervix, uterus and ovaries in all females independent of their reproductive status. Follicles and corpora lutea were clearly distinguishable in males, the accessory sexual glands and testes were visualized by transrectal and transcutaneous ultrasonography, respectively.
Due to the knowledge of the sonomorphology of the abdominal organs, it was possible to differentiate normal structures from pathologic alterations (i.e., nephropathy, nephromegaly, splenic myelolipoma, hydrosalpinx, endometrial cysts, cholecystopathy with gallbladder sediment). With the exception of one animal with clinical renal disease, all alterations described were incidental findings.
In conclusion, ultrasonography provides a diagnostic tool for visualization of the abdominal organs in cheetahs. In contrast with transcutaneous ultrasound, the advantages of the rectal application are detailed imaging of the ovaries including follicles and corpora lutea, and the ability to detect the nongravid uterus. Transrectal ultrasonography offers an accurate, non-invasive practical method for health monitoring and reproductive assessment in cheetahs and possibly in other endangered felid species.
LITERATURE CITED
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