A Review of the Impact of Neuter Status on Expression of Inherited Conditions in Dogs

Assisting decision-making on age of neutering for German Short/Wirehaired Pointer, Mastiff, Newfoundland, Rhodesian Ridgeback, Siberian Husky: associated joint disorders, cancers, and urinary incontinence

Spaying female and castrating male dogs, hereinafter referred to as neutering, is a US convention for the first year in the dog's life. Research on 35 breeds of dogs revealed that early neutering increases risks of joint disorders, such as hip dysplasia (HD), elbow dysplasia (ED), or cranial cruciate ligament (CCL) tear, or cancers, such as lymphosarcoma (LSA), mast cell tumor (MCT), hemangiosarcoma (has), or osteosarcoma (OSA), for some breeds. Joint disorder risks are heightened for some larger breeds and for mixed-breed dogs weighing more than 20 kg. Some breeds had elevated risks for cancers. Several other research teams have reported health complications associated with neutering. The study goal includes using the same methodology for data collection and analyses as in the study on 35 breeds for five additional dog breeds weighing at least 20 kg. The breeds were: German Short/Wirehaired Pointer, Mastiff, Newfoundland, Rhodesian Ridgeback, and Siberian Husky. Major differences among breeds appeared in vulnerability to joint disorders and cancers with early neutering: male and female Pointer breeds had elevated joint disorders and increased cancers; male Mastiff breeds had increased CCL and LSA and females had non-significant elevated CCL risks; female Newfoundland breeds had heightened risks for joint disorders and males had non-significant elevated risks; female Ridgeback breeds had heightened MCT with very early neutering; and Siberian Huskies showed no significant effects on joint disorders or cancers, but female breeds showed a non-significant but elevated CCL. Updated guidelines cover 40 dog breeds. These results further emphasize the importance of personalized decisions regarding the neutering of dogs, considering the dog's breed, sex, and context.

Factors related to longevity and mortality of dogs in Italy

Besides its translational value, an improved understanding of dog longevity and mortality is necessary to guide health management decisions, breed selection, and improve dog welfare. In order to analyse the lifespan of dogs in Italy, identify the most common causes of death, and evaluate possible risk factors, anonymised medical records were collected from 9 veterinary teaching hospitals and 2 public health institutions. Data regarding breed, sex, neuter status, age, diagnosis, and mechanism of death were retrieved. Cause of death (COD) was classified by pathophysiologic process (PP) and organ system (OS). Of the 4957 dogs that died between 2004 and 2020 included in the study, 2920 (59.0%) were purebred, 2293 (46.2%) were female, 3005 (60.6%) were intact, 2883 (58.2%) were euthanised. Overall median longevity was 10.0 years. Median longevity was significantly longer for crossbreds, females, neutered dogs, and small-sized breeds. The breeds with the highest median age at death were the Yorkshire terrier, English cocker spaniel, West Highland white terrier, Italian volpino, and Shih Tzu, whilst the American bulldog, English bulldog, American pit bull terrier, Bernese mountain dog and the Maremma and the Abruzzes sheepdog had the lowest median age at death. The most frequent COD by PP was neoplasia (34.0%), which occurred more frequently in large breeds, namely German shepherd, Labrador retriever and Boxer. Degenerative diseases mostly affected small-sized dogs like Miniature pinscher and Dachshund. Regarding the OS involved, diseases of the renal/urinary system were most frequently responsible for COD (15.0%), prevalently degenerative and inflammatory/infectious. Substantial variation in median longevity according to causes of death by PP and OS was observed. These data are relevant for breeders, veterinary practitioners, and owners, to assist breed selection, facilitate early diagnosis, guide choice when purchasing a purebred dog and making health management decisions, and ultimately improve dog welfare.

Castration promotes the browning of the prostate tumor microenvironment

BACKGROUND

Adipose tissue has gained attention due to its potential paracrine role. Periprostatic adipose tissue surrounds the prostate and the prostatic urethra, and it is an essential player in prostate cancer progression. Since obesity is directly related to human tumor progression, and adipose tissue depots are one of the significant components of the tumor microenvironment, the molecular mediators of the communication between adipocytes and epithelial cells are in the spotlight. Although periprostatic white adipose tissue contributes to prostate cancer progression, brown adipose tissue (BAT), which has beneficial effects in metabolic pathologies, has been scarcely investigated concerning cancer progression. Given that adipose tissue is a target of androgen signaling, the actual role of androgen removal on the periprostatic adipose tissue was the aim of this work.

METHODS

Surgical castration of the transgenic adenocarcinoma of the mouse prostate (TRAMP) was employed. By histology examination and software analysis, WAT and BAT tissue was quantified. 3T3-like adipocytes were used to study the role of Casodex® in modifying adipocyte differentiation and to investigate the function of the secretome of adipocytes on the proliferation of androgen-dependent and independent prostate cancer cells. Finally, the role of cell communication was assayed by TRAMP-C1 xenograft implanted in the presence of 3T3-like adipocytes.

RESULTS

Androgen removal increases brown/beige adipose tissue in the fat immediately surrounding the prostate glands of TRAMP mice, concomitant with an adjustment of the metabolism. Castration increases body temperature, respiratory exchange rate, and energy expenditure. Also, in vitro, it is described that blocking androgen signaling by Casodex® increases the uncoupling protein 1 (UCP1) marker in 3T3-like adipocytes. Finally, the effect of brown/beige adipocyte secretome was studied on the proliferation of prostate cancer cells in vivo and in vitro. The secretome of brown/beige adipocytes reduces the proliferation of prostate cancer cells mediated partly by the secretion of extracellular vesicles.

CONCLUSIONS

Consequently, we concluded that hampering androgen signaling plays a crucial role in the browning of the periprostatic adipose tissue. Also, the presence of brown adipocytes exhibits the opposite effect to that of white adipocytes in vitro regulating processes that govern the mechanisms of cell proliferation of prostate cancer cells. And finally, promoting the browning of adipose tissue in the periprostatic adipose tissue might be a way to handle prostate cancer cell progression. Video Abstract.

Common Orthopedic Traits and Screening for Breeding Programs

Orthopedic diseases are complex traits, meaning genetics and environmental factors affect risk, making identification of genetic associations difficult. In the United States, hip and elbow scores, patellar luxation scores, Legg-Calvé-Perthes disease, and shoulder osteochondrosis affectedness are available in the Orthopedic Foundation for Animals registry. Distraction indices and extended, ventrodorsal hip conformation scores are recorded by PennHIP. Application of estimated breeding values for hip and elbow dysplasia in breeder selection reduces the severity and prevalence of these traits. Genomic prediction and whole-genome sequence technologies and methods should improve knowledge of genetics underlying orthopedic diseases, leading to improved canine orthopedic genetic quality.

Body Condition and Fertility in Dogs

Ideal body condition and nutritional status in dogs is essential for quality of life, including reproductive health. Herein, we review the implications body condition, particularly fat, has on puberty, fertility, pregnancy, and parturition in dogs. Ideal body condition at puberty is necessary for dogs to achieve sexual maturity and reproduce. Moreover, over and under conditioned female dogs have increased risk of adverse pregnancy, parturition, and neonatal outcomes. Less is known about body condition and male dog fertility but some evidence is provided in this article. Finally, recommendations for maintaining an ideal body condition in intact adult dogs for optimal fertility are provided.

A Prospective Cohort Study Investigating the Impact of Neutering Bitches Prepubertally or Post-Pubertally on Physical Development

No previous large prospective cohort studies have been identified that have investigated the impact of the surgical neutering of bitches before or after known puberty on their growth and physical development. This study was designed to examine the data on physical development, vulval size, and conformation for bitches neutered by ovariohysterectomy before puberty (PPN, n = 155) or after puberty (control, n = 151) using a prospective cohort study design. Data were gathered at six- and 17-months of age using bespoke physical assessment forms and digital images of the vulva. PPN bitches had greater changes in height measurements (mean difference = 2.039, SEM = 0.334, 91% CI = 1.471 to 2.608, p < 0.001) and smaller changes in the measurements of vulval length (mean difference = -0.377, SEM = 0.079, 91% CI = -0.511 to -0.243, p < 0.001) and width (mean difference = -0.221, SEM = 0.063, 91% CI = -0.328 to -0.113, p < 0.001) between six- and 17-months of age than for the control bitches. Although not significant, the PPN bitches were taller (mean 58.5 vs. 56.6 cm) and heavier (mean 28.3 vs. 27.3 kg) with smaller vulval size measurements (mean vulval length 2.8 vs. 3.2 cm, mean vulval width 1.7 vs. 2.1 cm) at 17-months of age. At 17-months of age, significantly more PPN bitches had vulvas that appeared juvenile (Yates' Chi-square = 14.834, D.F. = 1, p < 0.001) and recessed (Yates' Chi-square = 7.792, D.F. = 1, p = 0.005) at the physical assessment, and significantly more PPN bitches had vulvas that appeared 'recessed/inverted' on the examination of digital images (Chi-square = 9.902, D.F. = 1, p = 0.002). The results from this study suggest no contraindications to prepubertal ovariohysterectomy for large breed bitches. However, any longer-term health implications of these differences in physical development need to be investigated and better understood prior to recommendations being made.

How size and genetic diversity shape lifespan across breeds of purebred dogs

While the lifespan advantage of small body size and mixed breed status has been documented repeatedly, evidence for an effect of genetic diversity across dog breeds is equivocal. We hypothesized that this might be due to a strong right-censoring bias in available breed-specific lifespan estimates where early-dying dogs from birth cohorts that have not died off completely at the time of data collection are sampled disproportionately, especially in breeds with rapidly growing populations. We took advantage of data on owner reported lifespan and cause of death from a large public database to quantify the effect of size and genetic diversity (heterozygosity) on mortality patterns across 118 breeds based on more than 40,000 dogs. After documenting and removing the right-censoring bias from the breed-specific lifespan estimates by including only completed birth cohorts in our analyses, we show that small size and genetic diversity are both linked to a significant increase in mean lifespan across breeds. To better understand the proximate mechanisms underlying these patterns, we then investigated two major mortality causes in dogs - the cumulative pathophysiologies of old age and cancer. Old age lifespan, as well as the percentage of old age mortality, decreased with increasing body size and increased with increasing genetic diversity. The lifespan of dogs dying of cancer followed the same patterns, but while large size significantly increased proportional cancer mortality, we could not detect a significant signal for lowered cancer mortality with increasing diversity. Our findings suggest that outcross programs will be beneficial for breed health and longevity. They also emphasize the need for high-quality mortality data for veterinary epidemiology as well as for developing the dog as a translational model for human geroscience.

Reproducibility and Feasibility of Classification and National Guidelines for Histological Diagnosis of Canine Mammary Gland Tumours: A Multi-Institutional Ring Study

Simple Summary

Tumours of the mammary gland are common in humans, as in canine species. They are very heterogenous with numerous morphological variants and different biologic behaviours. In the last few decades, several efforts have been made to classify these tumours histologically and establish the level of malignancy by using histologic grading systems. However, reproducibility and diagnostic agreement of such classification and grading have been only rarely assessed. In this study, we tested the variability in diagnoses performed by 15 pathologists using the same classification and grading system. Prior to the study, pathologists agreed on guidelines regarding how to apply these systems. Pathologists worked blindly on 36 digital histologic slides of canine mammary tumours. The agreement was statistically analysed using Cohen’s kappa coefficient that, when equal to 1, indicates perfect agreement. The overall agreement in the identification of hyperplastic-dysplastic/benign/malignant lesions was substantial (kappa 0.76), while outcomes on morphological classification had only a moderate agreement (k = 0.54). Tumour grade assigned by pathologists was the least concordant and kappa could not be calculated. Although promising, the results underline that each diagnostic/grading system should be assessed and optimized for standardization and high diagnostic agreement.

Abstract

Histological diagnosis of Canine Mammary Tumours (CMTs) provides the basis for proper treatment and follow-up. Nowadays, its accuracy is poorly understood and variable interpretation of histological criteria leads to a lack of standardisation and impossibility to compare studies. This study aimed to quantify the reproducibility of histological diagnosis and grading in CMTs. A blinded ring test on 36 CMTs was performed by 15 veterinary pathologists with different levels of education, after discussion of critical points on the Davis-Thompson Foundation Classification and providing consensus guidelines. Kappa statistics were used to compare the interobserver variability. The overall concordance rate of diagnostic interpretations of WP on identification of hyperplasia-dysplasia/benign/malignant lesions showed a substantial agreement (average k ranging from 0.66 to 0.82, with a k-combined of 0.76). Instead, outcomes on ICD-O-3.2 morphological code /diagnosis of histotype had only a moderate agreement (average k ranging from 0.44 and 0.64, with a k-combined of 0.54). The results demonstrated that standardised classification and consensus guidelines can produce moderate to substantial agreement; however, further efforts are needed to increase this agreement in distinguishing benign versus malignant lesions and in histological grading.

Cross Sectional Survey of Canine Idiopathic Epilepsy Management in Primary Care in the United Kingdom

The aims of this study are to gain insight on how primary care veterinarians in the UK diagnose and treat canine idiopathic epilepsy (IE) and what they perceive as challenges in the management of canine IE. Two hundred and thirty-five primary care veterinarians took part in this survey. The questionnaire asked about the type of practice the respondent worked in, any relevant post-graduate qualifications, how many years' experience they had in practice and the participant's canine IE caseload. Participants were asked how they diagnose canine IE, how they select antiseizure drugs (ASDs) and how they assess outcome. The questionnaire also explored which information sources they have access to for deciding on canine IE treatment, challenges that may be faced when managing these cases and areas in which more support can be provided. 94.5% of participants (n = 222/235) managed <10 canine IE cases in a year and 87.8% (n = 206/235) used phenobarbital as their first line ASD. The reported mean initial phenobarbital dose was 2.1 mg/kg (standard deviation = 0.71) every 12 h. When considering how closely participants aligned with IVETF guidelines on the topics of diagnosis, ASD initiation and outcome assessment, on average participants would score around half of the available points. 53.2% (n = 125/235) of respondents recommended neutering in canine IE and 46.8% (n = 110/235) did not. 53.2% (n = 125/235) did not recommend any additional treatments for canine IE beyond use of ASDs. 23.4% recommended Purina Neurocare diet (n = 55/235), 12.8% recommended environmental modification (n = 30/235), and 6.8% (n = 16/235) recommend medium chain triglyceride supplements. In this study participants found managing client expectations to be most challenging alongside canine IE emergency management. The main limitation of this study is the relatively low response rate and therefore the results may not reflect the entire small animal veterinary profession in the UK. However, the results of this study represent a starting point to inform educational resources and support strategies to improve quality care of canine IE in primary care.

Characterization of intestinal microbiota in normal weight and overweight Border Collie and Labrador Retriever dogs

Obesity in dogs is an emerging issue that affects canine health and well-being. Its development is ascribed to several factors, including genetic predisposition and dietary management, and recent evidence suggests that intestinal microbiota may be involved as well. Previous works have shown obesity to be linked to significant changes in gut microbiota composition in humans and mice, but only limited information is available on the role played by canine gut microbiota. The aim of this exploratory study was to investigate whether composition of canine faecal microbiota may be influenced by overweight condition and breed. All the enrolled companion dogs were young adults, intact, healthy, and fed commercial extruded pet food; none had received antibiotics, probiotics or immunosuppressant drugs in the previous six months. Labrador Retriever (LR) and Border Collie (BC) were chosen as reference breeds and Body Condition Score (BCS) on a 9-point scale as reference method for evaluating body fat. The faecal microbial communities of 15 lean (BCS 4-5/9; 7 LRs and 8 BCs) and 14 overweight (BCS > 5/9; 8 LRs and 6 BCs) family dogs were analysed using 16S rRNA gene sequencing. Moreover, for each dog, the daily intake of energy (kcal/d) and dietary macronutrients (g/d) were calculated according to an accurate feeding history collection. Firmicutes and Bacteroidetes resulted the predominant phyla (51.5 ± 10.0% and 33.4 ± 8.5%, respectively) in all dogs. Bioinformatic and statistical analysis revealed that no bacterial taxon differed significantly based on body condition, except for genus Allisonella (p < 0.05); BC gut microbiota was richer (p < 0.05) in bacteria belonging to phyla Actinobacteria (family Coriobacteriaceae in particular) and Firmicutes (Allobaculum and Roseburia genera). No remarkable differences were recorded either for diversity indices (i.e., alpha diversity, p > 0.10) or for divergence within the sample set (i.e., beta diversity, p > 0.05). PERMANOVA tests performed on single factors demonstrated the tendency of dietary protein to influence the recruited dogs' microbiota beta-diversity at amplicon sequence variant level (p = 0.08). In conclusion, the faecal microbiota of dogs involved in this exploratory study showed no major variations based on body condition. However, our findings suggested that certain bacterial taxa previously acknowledged in obesity-related studies may be detected in dissimilar amounts depending on canine breed.

Retrospective study of canine cutaneous tumors submitted to a diagnostic pathology laboratory in Northern Portugal (2014-2020)

Background

Cutaneous neoplastic diseases are the most and second-most frequently reported tumors in male and female dogs, respectively. The aims of this study were to report the occurrence of canine cutaneous tumors in a pathology laboratory located in Northern Portugal between 2014 and 2020, and to characterize and categorize the anatomical locations, breed, age, and sex of the animals affected with different types of neoplasms.

Results

Throughout the 7-year study, 1,185 cases were diagnosed as cutaneous tumors, with 62.9% being classified as benign, and 37.1% as malignant. Mast cell tumors (22.7%) were the most frequently diagnosed tumor type, followed by benign soft tissue tumors (9.7%), sebaceous gland tumors (8.1%), vascular tumors (7.9%) and soft tissue sarcomas (7.6%). Cutaneous tumors commonly exhibited multicentric occurrence (14.6%) followed by single occurrence in hindlimb (12.1%), forelimb (8.6%), buttock (7.1%), abdominal (6.5%) and costal (5.2%) areas. The odds of developing cutaneous neoplasia were higher with increasing age (p < 0.001). Females had an increased odds of developing skin tumors compared to males (crude OR = 2.99, 95% (2.51, 3.55); adj OR = 2.93, 95% (2.46, 3.49). Purebred dogs, as a group, showed a reduced odds of developing cutaneous tumors when compared to mixed-breed dogs (crude OR = 0.63, 95% (0.53, 0.74); adj OR = 0.75, 95% (0.62, 0.89).

Conclusions

Mast cell tumors, benign soft tissue tumors and sebaceous tumors were the most common histotypes encountered. The epidemiological survey achieved with this study demonstrates the relative frequency of different types of tumors in this particular population. Furthermore, the results herein achieved can act as a basis or a beneficial reference for local veterinarians helping in the establishment of a preliminary and presumptive diagnosis of canine cutaneous tumors histotypes.

Plain English summary

Skin tumors are the most and second-most frequently reported tumors in male and female dogs, respectively. The aim of this study was to report the occurrence of canine skin tumors in a diagnostic pathology laboratory located in Northern Portugal, between 2014–2020 and to characterize the anatomical distributions, breed, age, and sex of the animals affected by different skin tumors.

During this period, 1,185 cases were diagnosed as skin tumors; 62.9% were diagnosed as benign, while 37.1% were malignant. Mast cell tumors (22.7%) were the most frequently diagnosed neoplasia, followed by benign soft tissue tumors (9.7%), sebaceous gland tumors (8.1%), vascular tumors (7.9%) and soft tissue sarcomas (7.6%). Skin tumors commonly developed in more than one location (14.6%) followed by solitary development in hindlimb (12.1%), forelimb (8.6%), buttock (7.1%), abdominal (6.5%) and costal (5.2%) areas. An increased odds of developing skin neoplasms as the patient’s age increase was detected. Females showed an increased odds in comparison to male dogs. Purebred dogs presented decreased odds for developing skin tumors in comparison to mixed-breed dogs.

The information relevance achieved with this study demonstrates the relative frequency of different types of tumors in this particular population, acting as a basis or a beneficial reference for regional veterinarians when providing an initial diagnosis of canine skin tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40575-022-00113-w.

Phenotypic characterization of idiopathic epilepsy and epilepsy of unknown cause in Irish Setters

Canine epileptic seizures are common neurological symptom presenting to veterinary practice. Idiopathic epilepsy (IE) with a suspected genetic background has been reported in several dog breeds. Although it has been reported in the Irish Setter (IS), the phenotypic characteristics have not yet been described. The aim of this study was to characterize the phenotype of IE in this breed and to trace its mode of inheritance. Owners of IS were requested to fill in a questionnaire via the Dutch Irish Setter Club concerning the epileptic seizures in their dogs. The data was assessed retrospectively using descriptive statistics. Forty-eight privately owned IS dogs fulfilling tier I criteria for IE according to the International Veterinary Epilepsy Task Force of both sexes were included in the study. The mean age of seizure onset was 41 months. Five of the dogs included in the study had an onset of seizures >6 years of age. These dogs were classified with epilepsy of unknown cause (EUC). Primary generalized tonic-clonic seizures were the most common type of seizure and were seen in almost all dogs. Cluster seizures were reported in 54% of the studied population. Most owners reported pre- (56%) and post-ictal (97%) signs in their dogs. A pedigree analysis of one subpopulation was performed and traced the lineage of 13 affected IS. A segregation analysis of this population rejected a simple autosomal recessive inheritance pattern. The present study supports the occurrence of IE and EUC in the IS. The results provide clinical insight into epileptic seizures in this breed and may be a starting point for further, including genetic, analysis.

2021 AAHA Working, Assistance, and Therapy Dog Guidelines

The guidelines are the first comprehensive consensus report on veterinary healthcare recommendations for working, assistance, and therapy dogs. This category of canine patients includes a broad assortment of animals, some with well-defined functions and others that provide a more generalized support role. The guidelines discuss recommendations for dogs trained for protection, odor/scent detection, service functions for people with diagnosed disabilities or physical limitations, emotional support, and therapeutic intervention. Although the term is often used to describe dogs providing animal-assisted activities, true therapy dogs provide goal-directed therapy, often under the supervision of a healthcare professional such as an occupational therapist or psychologist. Many working dogs undergo extensive training and have rigorous physical demands placed upon them. These factors make working, assistance, and therapy dogs inherently valuable and impose a need for a high level of primary veterinary care as described in the guidelines. Because working dogs have a particularly close relationship with their handlers, a trust relationship between the practice team and the working-dog client is imperative.

Keratoconjunctivitis sicca in dogs under primary veterinary care in the UK: an epidemiological study

OBJECTIVES

To estimate the frequency and breed-related risk factors for keratoconjunctivitis sicca (KCS) in dogs under UK primary veterinary care.

METHODS

Analysis of cohort electronic patient record data through the VetCompass Programme. Risk factor analysis used multivariable logistic regression.

RESULTS

There were 1456 KCS cases overall from 363,898 dogs [prevalence 0.40%, 95% confidence interval (CI) 0.38-0.42] and 430 incident cases during 2013 (1-year incidence risk 0.12%, 95% CI 0.11-0.13). Compared with crossbreds, breeds with the highest odds ratio (aOR) for KCS included American cocker spaniel (aOR 52.33: 95% CI 30.65-89.37), English bulldog (aOR 37.95: 95% CI 26.54-54.28), pug (aOR 22.09: 95% CI 15.15-32.2) and Lhasa apso (aOR 21.58: 95% CI 16.29-28.57). Conversely, Labrador retrievers (aOR 0.23: 95% CI 0.1-0.52) and border collie (aOR 0.30: 95% CI 0.11-0.82) had reduced odds. Brachycephalic dogs had 3.63 (95% CI 3.24-4.07) times odds compared to mesocephalics. Spaniels had 3.03 (95% CI 2.69-3.40) times odds compared to non-spaniels. Dogs weighing at or above the mean bodyweight for breed/sex had 1.25 (95% CI 1.12-1.39) times odds compared to body weights below. Advancing age was strongly associated with increased odds.

CLINICAL SIGNIFICANCE

Quantitative tear tests are recommended within yearly health examinations for breeds with evidence of predisposition to KCS and might also be considered in the future within eye testing for breeding in predisposed breeds. Breed predisposition to KCS suggests that breeding strategies could aim to reduce extremes of facial conformation.

Most Dogs Are Not NATIVE Dogs

Studies of dogs have proliferated among canine scientists, aided in part by the logistical convenience of working with owned animals whose care is handled by others. These pet dogs are unlike most dogs that have lived in contemporary or prehistoric settings. In particular, many of the dogs studied by canine scientists are NATIVE dogs: (1) neutered, (2) alimented, (3) trained, (4) isolated, (5) vaccinated, and (6) engineered. The distinct genotypes and unusual environments of NATIVE dogs stand in contrast to the characteristics of dogs who have adapted to lives in other human communities and settings. For a holistic perspective on the evolution of dogs, it is helpful to study dogs in environments that share features of the settings in which dogs evolved.

Ovarian Cysts in the Bitch: An Update

Functional ovarian cysts occur as solitary or multiple fluid-filled structures of variable size that are unilateral or bilateral in the bitches of age 6-8 years. Though the pathogenesis is obscure, insufficient LH surge, intrafollicular changes in gonadotrophin receptors and growth factors are the possible reasons behind the occurrence of hormonally active ovarian cysts that predisposes the bitch to the development of cystic endometrial hyperplasia-pyometra complex and occasionally hyper estrogenism. In the presence of suggestive signs, ultrasonography is the practical imaging modality for the clinical diagnosis that can be confirmed by assay of ovarian steroids and histopathology. Medical management with gonadotrophin-releasing hormone analogues and human chorionic gonadotrophin is not preferred as they are not always successful. As uterine pathologies are highly likely by the time of diagnosis, ovariohysterectomy is the treatment of choice for the follicular and luteal cysts. Understanding the cellular and molecular changes in the hypothalamo-hypophyseal ovarian axis will improve our understanding on the canine ovarian cysts.

Gonadotropin-Releasing Hormone (GnRH) Agonist Implants for Male Dog Fertility Suppression: A Review of Mode of Action, Efficacy, Safety, and Uses

At present, only surgical sterilization is available for veterinarians and pet owners seeking suppression of fertility in male dogs, in most countries. An alternative contraceptive alternative approach is GnRH releasing implants that desensitize the pituitary to the stimulatory effects of GnRH and thereby block testicular function (testosterone and sperm production). Two GnRH agonists (deslorelin and azagly-nafarelin) have been researched in controlled release formulations for this purpose. A deslorelin-releasing biodegradable implant, marketed under the name Suprelorin®, has been available in Australia and New Zealand since 2007, the European Union (EU) since 2008, and received regulatory approval in China and Mexico in late 2019. Two versions of the implant are available, one labeled for a minimum of 6 months of fertility suppression in male dogs, and the other for a minimum of 12 months in male dogs. Another GnRH agonist (azagly-nafarelin) was also included in a solid implant (Gonazon®). Research results showed it delivered 6-months to 1 year of suppressed fertility; however, it is not commercialized. This review paper summarizes research on the mechanism of action for these technologies and compiles and interprets the research on efficacy and safety. New findings on usage of the deslorelin releasing implant in countries where veterinarians and pet owners have this option is shared. Research on off-label use of the product in male dogs is also reviewed. This review aims to aid in the evaluation of the deslorelin releasing implant as an adjunct or alternative for surgical sterilization of male dogs.