Disorders of sexual development in the cat: Current state of knowledge and diagnostic approach

Unusual sex chromosomal DSD in a domestic Shorthair cat with a 37,X/38,XY mosaic karyotype

BACKGROUND

Sex chromosome abnormalities associated with disorders of sexual development (DSD) are rarely described in cats, mainly due to the lack of chromossome studies that precisely reveal the condition. Genetic approaches are therefore required in order to detect sex chromossomes abnormalities as variations in the number and structure of chromosomes, or the presence of a second cell line as mosaicim or chimerism.

CASE PRESENTATION

A male Shorthair cryptorchid cat was presented with clinical signs of anorexia, tenesmus and hyperthermia. Ultrasonography revealed a fluid-filled structure, with approximately 1 cm in diameter, adjacent to the descending colon. Computed tomography evidenced a tubular structure, ventral to the descending colon and caudal to the bladder, which extended cranially, through two branches. Histopathological evaluation confirmed the presence of two atrophic uterine horns and one hypoplastic testicle with epididymis at the end of one of the uterine horns. The end of the other uterine horn was attached to a structure composed by a mass of adipocytes. Cytogenetic analysis revealed a mosaic 37,X/38,XY karyotype. The two cell lines were found in 15% and 85% of the lymphocytes, respectively. Genetic analysis confirmed the presence of SRY and ZFY genes in blood and hair bulbs, and revealed a marked reduction in SRY expression in the testicle. Additionally, this case presented exceptionally rare features, such as a Leydig' cell tumour and a chronic endometritis in both uterine horns.

CONCLUSIONS

Complete imaging workup, cytogenetic analysis and SRY gene expression should be systematically realized, in order to properly classify disorders of sexual development (DSD) in cats.

Segmental aplasia of the paramesonephric duct in a New Zealand white rabbit and a review of the literature

In females, the paramesonephric (syn: Müllerian) duct gives rise to the uterine tubes, uterus, cervix, and part of the vagina. Segmental uterine aplasia resulting from a paramesonephric duct abnormality has been reported in a range of species including bovids, canids, felids, equids, camelids, and lagomorphs. Here we document segmental aplasia of the left paramesonephric duct in a New Zealand white rabbit. The proximal 70 mm of the left uterine tube was present and terminated in adipose tissue. A 10 × 2 × 1-mm tag of cream tissue was present and was composed of sheets of adipose tissue and streams of smooth muscle, but otherwise, there was no evidence of the left uterine horn, supporting a diagnosis of unilateral uterine aplasia (uterus unicornis) analogous to a human class II (unicornuate uterus) lesion of the "no horn" subtype. In addition, our case had a concurrent uterine tube fimbrial cyst, minor cysts in the left kidney, and mammary gland hyperplasia with secretory activity. We suggest the adoption of a uniform classification system specifically for lagomorph uterine anomalies. Large-scale multi-center studies documenting prevalence of such lesions would facilitate identification of trends in laterality and other factors.

Cytogenetic and molecular insight into the genetic background of disorders of sex development in seventeen cats

The genetic background of feline disorders of sex development (DSDs) is poorly understood. We performed comprehensive cytogenetic, molecular, and histological studies of 17 cats with abnormal external genitalia, unusual behavior, or tricolor coats (atypical in males). The DSD phenotype of three cats was associated with sex chromosome abnormalities: X/Y translocation (38,XX^SRY+), 37,X/38,XY mosaicism, and XX/XY leukocyte chimerism. The remaining 14 affected cats were classified as XY DSD (SRY-positive). In this group and 38 normal males, we analyzed a priori selected candidate genes (SRY, TAC3, CYP11B1 and LHCGR). Only a previously reported nonpathogenic variant was found in SRY. Moreover, SRY gene copy number was determined, and three variants were observed: 6, 5 (modal), and 4 copies in a single DSD case. The known variants in TAC3 and CYP11B1, responsible for testicular hypoplasia, persistent primary dentition or congenital adrenal hyperplasia, were not found in the study group. Nine novel polymorphisms were identified in the LHCGR gene, one of which, a potentially regulatory indel variant in 5'UTR, was significantly associated (p = 0.0467) with XY DSD. Our report confirmed that abnormalities of sex chromosomes are important causes of feline DSDs. We also showed that the indel variant of LHCGR can be considered a promising marker associated with XY DSD phenotype.

Reproductive Management in Catteries: Optimising health and wellbeing through veterinarian-breeder collaboration

PRACTICAL RELEVANCE

Many veterinarians - even those engaged in small animal reproduction - are uncomfortable with taking care of cat breeders or being in charge of catteries. Likely reasons for this are that feline reproduction is largely under-represented in undergraduate and graduate reproduction teaching, as well as in postgraduate education and science, whereas cat breeders themselves are often well informed and actively share knowledge with other cat breeders via the internet and social media.

CLINICAL CHALLENGES

A variety of problems can exist within a cattery, and collaboration between veterinarian and breeder to solve these is ultimately beneficial for the breeder, for the veterinarian, and for the health and wellbeing of the individual cats and of the cattery as a whole.

AIM

This review presents a comprehensive overview of aspects of cattery management that might negatively impact reproduction, including sanitation, hygiene and infectious disease control. It also discusses monitoring of reproductive performance, breeding recommendations, and the diagnostic and therapeutic approach to some common and specific problems.

EQUIPMENT AND TECHNICAL SKILLS

Reproductive management in the cattery requires no specialised equipment, as such. What it does need is an open mind, in terms of seeing how things are done, an open ear, for listening to the breeder, and the veterinarian's clinical skills in palpation, auscultation and, where required, further examination of the animals. Keeping abreast of the latest information on infectious diseases, disinfection and genetics ensures proper advice is provided.

EVIDENCE BASE

Current knowledge of reproductive management in catteries is summarised in order to apply an evidence-based approach, whenever possible. Notwithstanding, much of the information remains empirical.

Infertility In Toms: Clinical approach, experiences and challenges

PRACTICAL RELEVANCE

An infertile tom used to be a relatively rare presentation in feline practice. However, as a result of breeding strategies targeting specific morphological/behavioural traits, and the influence of inbreeding (especially practised in rare breeds), among other factors, feline infertility has become a genuine clinical problem. Furthermore, increased interest among cat breeders and pet owners in diagnosing and treating an 'unsuccessful' tom (including using assisted reproductive techniques [ARTs]), has made such patients more commonplace in veterinary practice.

CLINICAL CHALLENGES

A definitive cause for male infertility is often difficult to identify. One of the biggest challenges is the lack of fertility-based reference values for semen quality and hormone levels. Moreover, the literature in this field is scant and many reproductive tract conditions described in other species have not been reported in cats. The establishment of diagnostic tools and algorithms is essential to facilitate a reliable assessment of fertility potential.

GLOBAL IMPORTANCE

There is a growing demand for appropriate veterinary care relating to feline reproduction. There is an expectation among breeders, particularly of pedigree cats of high breeding value, that the same options widely used for dogs (including ARTs) should also be available for cats.

EQUIPMENT AND TECHNICAL SKILLS

Equipment required for investigating male infertility includes a microscope and ultrasound machine; a blood analyser may also be useful, but samples can instead be sent to a laboratory. The skills required are often already performed by veterinarians; for example, catheterising the urethra, performing ultrasonography and blood sampling.

EVIDENCE BASE

There are some reports of fertility problems in male cats in the literature, but this area of feline reproduction is still relatively undeveloped. This review draws on the comprehensive knowledge developed and shared by specialists in this field, and is supported by the authors' own clinical experience.

Infertility In Queens: Clinical approach, experiences and challenges

CLINICAL CHALLENGES

It is not easy for a veterinarian to determine the cause of infertility in a queen. The simplest method is to start by investigating the most common causes and then progress by successive elimination to the less common causes. For example, mating problems are commonly responsible for reproductive failure, and owners should be particularly vigilant in checking that the mating is progressing satisfactorily. Frequently, a veterinarian may have to determine, among other things, if there is a uterine or hormonal disorder or if an infectious pathology may be involved. In the case of a queen that is not cycling, it is important to differentiate a lack of onset of puberty in a young queen from a lack of cyclicity in an adult queen.

AIM

This review sets out a practical, step-by-step approach that veterinarians can follow, starting with the most common causes of infertility in queens and moving towards more rare or specific causes.

EQUIPMENT AND TECHNICAL SKILLS

Simple techniques such as vaginal smears are essential to determine if a queen that is ready to be mated is in full oestrus, if a queen is cycling or not and to diagnose inflammation of the genital tract. Veterinarians should be familiar with the peculiarities of the swabbing technique in cats, as well as the interpretation of feline vaginal cytology. Progesterone assays are useful on many occasions in the diagnosis pathway. A laboratory capable of performing karyotypes should ideally be available. Finally, it is important to be able to perform an ultrasound examination of the ovaries and uterus in a queen.

EVIDENCE BASE

Although it appears that infertility is a problem among purebred queens, there is a lack of knowledge in this area and too few published studies. Some causes of feline infertility remain poorly investigated.