Pathology: Reproduction

Key Abbreviations in Animal Reproductive Health

• SMEDI: Stillbirth, Mummification, Embryonic Death, Infertility.
• ACA: Adenocarcinoma.
• AI: Artificial Insemination.
• BPH: Benign Prostatic Hyperplasia.
• BVD: Bovine Viral Diarrhoea.
• CAEV: Caprine Arthritis and Encephalitis Virus.
• CBC: Complete Blood Count.
• CEH: Cystic Endometrial Hyperplasia.
• CFT: Complement Fixation Test.
• CNS: Central Nervous System.
• DSD: Disorder of Sexual Development.
• EED: Early Embryonic Death.
• EHV-1: Equine Herpes Virus 1.
• FSH: Follicle-Stimulating Hormone.
• GDT: Gel Diffusion Test.
• GnRH: Gonadotropin-Releasing Hormone.
• LH: Luteinizing Hormone.
• MPI: Ministry for Primary Industries.
• PCR: Polymerase Chain Reaction.
• PU/PD: Polyuria/Polydipsia.
• RFM: Retained Fetal Membranes.
• SCC: Squamous Cell Carcinoma/Somatic Cell Count.
• Serology: Identification of antibodies in body fluids.
• TCC: Transitional Cell Carcinoma.
• TDF: Testis Determining Factor.
• U/A: Urinalysis.
• USG: Urine Specific Gravity.
• UTI: Urinary Tract Infection.

Overview of Domestic Animal Reproductive System

• Classified into five categories: DSDs, maladies of male and female genital systems, pregnancy failures (infertility, abortion, perinatal mortality), and mammary gland diseases.
• Reproductive system pathology is complex due to variations between sexes and species.

Disorders of Sexual Development (DSDs)

• DSDs categorized by chromosome type (XX, XY), presence of SRY, gonadal type, and appearance of genitalia.
• Terms like "intersex" and "hermaphrodite" still in use.
• Freemartins are chimeras, mainly observed in females co-twin to males, often infertile, with abnormal reproductive organs.

Male Genital System Diseases

• Male reproductive functions include testosterone production and sperm development, essential for breeding success.
• Disorders can emerge from three anatomical regions: scrotum and its contents, accessory sex glands, penis, and prepuce.

Scrotum, Testes, and Epididymis

• Testes must remain cooler than body temperature for effective spermatogenesis.
• Scrotal dermatitis can lead to infertility via increased testicular temperature; often caused by Chorioptes bovis in sheep.
• Cryptorchidism: Incomplete testis descent, risky for infertility and neoplasia—castration is advised.
• Small testes: Can be due to hypoplasia (failure to grow) or atrophy (decrease after puberty) resulting from various factors including toxins.
• Epididymitis: Common inflammation mostly in rams and dogs; can cause infertility. Key causes: Brucella ovis and gram-negative bacteria like Actinobacillus seminis.

Female Genital System Diseases

• Uterine function critical for fetal development; needs to be a sterile environment.
• Infections can enter via the cervix, significantly impacting fertility.

Uterine Position Changes

• Torsion: Uncommon but may occur in heavily pregnant cows. Sudden torsions can invoke severe complications.
• Rupture: Can happen from torsion or dystocia, often fatal.
• Prolapse: Common post-parturition in cows, sows, and ewes; prolonged straining and flaccid uterus lead to this condition.

Retained Fetal Membranes (RFM)

• RFM refers to membranes retained over 24 hours post-parturition. Major causes include dystocia and uterine infections, leading to possible severe complications like metritis.

Endometritis and Metritis

• Endometritis: Inflammation primarily of the inner layer, often mild with minimal external signs.
• Metritis: Involves the entire uterine wall, typically presents with severe clinical symptoms. Can progress to pyometra and significantly alter fertility.

Important Considerations

• Identifying and correcting male infertility issues are crucial for herd productivity.
• DSDs can introduce complexities in breeding strategies and require careful diagnostic approaches.### Causes of Metritis and Endometritis
• Ascending bacterial infection is the primary cause of metritis across species, significantly influenced by factors like open cervix and dystocia.
• Common bacteria involved include Trueperella pyogenes, Staphylococcus, Streptococcus, and coliforms, particularly in postpartum cows.
• Non-specific metritis often seen in cows post-partum, with variable uterine appearance based on disease severity.

Diagnosis of Endometritis in Cattle

• Metrichecking utilizes a silicon cup to collect vaginal mucus for examination, assessing consistency, color, and odor.
• Clear, odourless discharge indicates better fertility; turbid, purulent, or bloody discharges signify endometritis and possible infertility.

Diagnosis of Endometritis in Mares

• Endometrial biopsy is essential in identifying issues and infertility in mares, guided by rectal palpation to collect a small uterine sample.

Canine Pyometra

• Pyometra, often related to prior estrogen administration in young dogs, presents with clinical signs of toxaemia including depression, anorexia, and fever.
• Often leads to serious complications requiring surgical intervention; commonly diagnosed through imaging revealing uterine enlargement.

Diagnosis and Clinical Pathology of Canine Pyometra

• Characterized by marked neutrophilia and possible dehydration indicators; sepsis-related changes like hypoglycemia may also be present.
• Diagnosis may involve histological evidence of protozoal organisms in tissues.

Salmonella Brandenburg in Ovine Abortions

• Identified in sheep abortions in New Zealand since 1996, with significant outbreaks causing heavy losses in late gestation.
• Affected fetuses show signs of autolysis; confirmed via culture of fetal stomach contents or placental tissues.

Other Bacterial Abortions in Sheep

• Bacterial infections, often sporadic, arise from Yersinia, Pasteurella, and Listeria spp.; Listeria linked to spoiled silage.
• Diagnosis through culture/PCR from fetal samples; gross lesions may not always be visible.

Chlamydia Pecorum in Sheep

• Emerging cause of abortion outbreaks since 2018, presenting in late gestation without significant gross lesions in affected fetuses.
• Definitive diagnosis relies on PCR testing of fetal tissues.

Common Causes of Abortion in Ovine Species

• Campylobacter fetus, Toxoplasma gondii, and various bacteria including Salmonella are the main agents contributing to abortion.
• Vaccination options for Campylobacter, Toxoplasma, and Salmonella exist and should be discussed with owners.

Stress-Induced Abortion in Goats

• Goats are particularly susceptible to stress-related abortions, especially during late gestation; factors include undernutrition and adverse weather.
• Diagnosis largely circumstantial, with fresh fetal expulsion being indicative.

Toxoplasma Gondii in Goats

• Similar to sheep, but placental lesions may be milder and harder to detect, complicating diagnosis.

Equine Abortion Causes

• Twinning, umbilical cord abnormalities, and bacterial infections are significant factors.
• Umbilical cord torsion risks fetal death by compromising the umbilical vessels.

Bacterial Abortions in Horses

• Ascending infections commonly lead to abortion via bacteria like Streptococcus and E. coli.
• Diagnosing bacterial abortions can be complicated due to common environmental contaminants.

Equine Herpesvirus 1 (EHV-1)

• A critical cause of abortion in mares, EHV-1 infects the respiratory tract and can lead to uterine infection.
• Diagnosis is generally supported by high or rising antibody titers post-abortion.

General Overview of Mastitis

• Mastitis is inflammation of the mammary gland, primarily significant in dairy cattle.
• Initial stages include invasion, infection, and inflammation, typically via ascending bacterial infection.

Clinical vs. Subclinical Mastitis

• Clinical mastitis displays overt signs such as abnormal milk and udder swelling, while subclinical mastitis is asymptomatic and diagnosed through tests like high somatic cell counts.
• Management is crucial as mastitis can lead to varying outcomes including animal death, chronic conditions, or resolution of infection.

Highlights of Mastitis Pathogenesis

• Effective resistance declines as lactational age increases, influenced by gland defenses and milking practices.
• Diagnosis relies on detection of leukocytes and bacteria, often requiring culture for confirmation.

Bovine Mastitis

• Causes significant economic losses and accounts for a large proportion of antibiotic use in livestock.
• Most prevalent around calving and drying-off periods.
• Differentiates between clinical mastitis (evident changes) and subclinical mastitis (requires additional testing to diagnose).
• Localized infections often affect 1-2 quarters due to anatomical and physiological barriers.
• Pathogenic bacteria are categorized into cow-associated (contagious) and environmental sources.

Contagious Bacteria

• Involves pathogens such as Staphylococcus aureus and Streptococcus agalactiae.
• Typically reside on udder and teat skin, spreading during milking via galactogenous routes.
• Severe cases manifest as clinical mastitis with gland swelling, redness, and necrosis, known as "gangrenous" mastitis.
• Systemic signs include fever, diarrhea, recumbency, and potential death.

Environmental Bacteria

• Common pathogens include Streptococcus uberis, Streptococcus dysgalactiae, and coliforms like E. coli.
• Primarily sourced from the environment (e.g., feces, mud), infections enter through the teat canal during milking.
• Similar to contagious infections, severe environmental infections show systemic illness and may lead to necrosis and death.

Mycoplasma bovis Mastitis

• Associated with "refractory mastitis" that does not respond well to standard treatments.
• Signs include reduced milk production, swollen udder, and poor response to antibiotics due to the absence of a cell wall in the bacterium.
• Also linked to other syndromes like arthritis and respiratory issues in calves.

Clinical Pathology Findings

• Severe clinical mastitis may show inflammatory leukogram, neutropenia, and toxic changes.
• Common findings include systemic clinical signs indicating necrotizing infections.

Mastitis in Sheep and Goats

• Caused by bacteria like Staphylococcus aureus and Mannheimia haemolytica, often leading to acute necrotizing mastitis.
• Infection typically affects one gland, with symptoms including swollen and discolored udder, and severe systemic signs that might result in death.
• In goats, udder issues may relate to caprine arthritis and encephalitis virus infection.

Clinical Signs in Mammary Diseases

• Gangrenous mastitis shows a clear demarcation line in affected tissues, indicating necrosis.
• In sheep, primary pathogens such as Staphylococcus aureus lead to similar symptoms as in cattle.

Mastitis in Small Animals (Cats and Dogs)

• Uncommon yet significant, usually occurring postpartum in early lactation in dogs.
• Common pathogens include Staphylococcus spp., Streptococcus spp., and E. coli.
• Symptoms of acute mastitis involve warmth, swelling, pain in affected glands, and potential systemic signs like fever.

Mammary Neoplasia in Dogs

• Common in middle-aged or older intact bitches; late speying increases risk.
• Tumours can be benign or malignant, with a higher benign rate in early speyed populations.
• Malignant tumours present as larger masses (>5cm), with a tendency to invade local tissues and lymph nodes.

Mammary Neoplasia in Cats

• Less frequent than in dogs; a high proportion (up to 90%) of neoplasms are malignant adenocarcinomas.
• Rapid growth and metastasis characterize these tumours, particularly prevalent in Siamese breeds.

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