Infectious Abortions (Brucella canis, Campylobacter, Feline Herpesvirus-1, Feline Infectious Peritonitis, Toxoplasma)

Infectious abortions in small animal theriogenology refer to the premature termination of pregnancy (resorption, abortion, or stillbirth) caused by specific infectious agents that disrupt the maternal-fetal unit, leading to embryonic or fetal death and expulsion. In dogs and cats, the most clinically significant infectious causes include Brucella canis (a zoonotic Gram-negative intracellular bacterium), Campylobacter species (enteric pathogens), Feline Herpesvirus-1 (FHV-1, a ubiquitous alphaherpesvirus), Feline Infectious Peritonitis virus (FIP, a mutated feline coronavirus), and Toxoplasma gondii (an obligate intracellular protozoan). These agents induce abortion through diverse mechanisms: direct fetal infection and necrosis, placental insufficiency, endometrial damage, systemic maternal illness, or immune-mediated fetal rejection. The clinical presentation ranges from early embryonic resorption with no visible signs to late-term abortion with fetal expulsion, often accompanied by vaginal discharge, systemic signs, and infertility. Accurate diagnosis is critical due to zoonotic potential (Brucella, Campylobacter, Toxoplasma) and the need for targeted antimicrobial or antiviral therapy, as well as biosecurity measures. This entry provides an encyclopedic overview of the etiopathogenesis, clinical features, diagnostic workup, and therapeutic management of these infectious abortifacients in canine and feline patients.

The primary infectious agents causing abortion in dogs and cats are:

1. **Brucella canis**: A small, Gram-negative, facultative intracellular coccobacillus. It is the most common bacterial cause of abortion in dogs worldwide. The organism has a predilection for the reproductive tract, particularly the uterus, placenta, and fetal tissues. It survives within macrophages and reticuloendothelial cells, evading immune clearance. Transmission occurs venereally, or via contact with aborted fetuses, placental fluids, and vaginal discharges. The bacterium is zoonotic, posing a risk to humans.

2. **Campylobacter species**: Primarily Campylobacter jejuni and C. upsaliensis, Gram-negative, microaerophilic, spiral-shaped bacteria. They are enteric pathogens in dogs and cats, but can cause abortion, especially in immunocompromised or stressed animals. The mechanism is likely bacteremia and placental colonization, leading to placentitis and fetal death. Zoonotic potential exists.

3. **Feline Herpesvirus-1 (FHV-1)**: An enveloped, double-stranded DNA alphaherpesvirus. It is a major cause of upper respiratory disease in cats (feline viral rhinotracheitis). During viremia, the virus can cross the placenta, causing fetal infection, necrosis, and abortion, particularly in primary infections during pregnancy. Latency in trigeminal ganglia and reactivation under stress are key features.

4. **Feline Infectious Peritonitis virus (FIP)**: A mutated form of feline enteric coronavirus (FECV). The mutation enables the virus to replicate efficiently in macrophages, leading to systemic granulomatous disease (FIP). Pregnant queens with FIP may abort due to severe systemic illness, vasculitis, and placentitis. The virus is not directly abortifacient but causes maternal debilitation and placental dysfunction.

5. **Toxoplasma gondii**: An obligate intracellular protozoan parasite. Cats are the definitive host, shedding oocysts in feces. Ingestion of oocysts or tissue cysts (from intermediate hosts) leads to systemic infection. During pregnancy, tachyzoites can cross the placenta, causing fetal infection, necrosis, and abortion. Toxoplasmosis is zoonotic, with serious implications for immunocompromised humans and fetuses.

Infectious abortions occur sporadically or as outbreaks in breeding kennels and catteries.

- **Brucella canis**: Endemic in many regions, with higher prevalence in stray and shelter dogs. Seroprevalence varies from 1-8% in some populations, but can be higher in breeding facilities. All breeds are susceptible, but sexually intact dogs are at risk. Transmission is primarily venereal, but also occurs through contact with aborted materials. The disease is chronic and can persist for years.

- **Campylobacter**: Common in young dogs and cats, especially in crowded environments. Abortion is rare but may occur in pregnant females with concurrent immunosuppression or stress. Prevalence of fecal shedding is high (up to 50% in some shelter populations).

- **FHV-1**: Highly prevalent in multi-cat households and shelters. Seroprevalence exceeds 90% in some populations. Abortion is most common in queens with primary infection during pregnancy, especially in the first half of gestation. Latent infections can reactivate under stress, but abortion is less common in recurrent infections.

- **FIP**: Occurs in cats of all ages, but abortion is a rare manifestation. The disease is more common in purebred cats and those from high-density environments. The incidence of FIP is low (1-5% of FECV-infected cats), but abortion may occur in queens with systemic disease.

- **Toxoplasma gondii**: Seroprevalence in cats varies widely (10-80%) depending on lifestyle. Outdoor cats are more likely to be infected. Abortion is uncommon, but can occur in primary infections during pregnancy. The risk of transplacental transmission is highest in the first and second trimesters.

The pathophysiological mechanisms differ among agents:

- **Brucella canis**: After entry, the bacterium localizes in regional lymph nodes, then spreads hematogenously to the uterus, placenta, and fetal tissues. It has a tropism for erythritol, a sugar alcohol present in the placenta of dogs, which promotes its growth. The organism causes placentitis, with necrosis and inflammation of the chorionic villi, leading to placental separation and fetal hypoxia. It also induces a chronic inflammatory response, with mononuclear cell infiltration and fibrosis. Abortion typically occurs between days 45-59 of gestation, often with the birth of stillborn or weak puppies. The bacterium persists in the uterus and epididymis, causing chronic infection and infertility.

- **Campylobacter**: The bacteria colonize the intestinal tract, causing enteritis. In pregnant animals, bacteremia can occur, leading to placental colonization. The resulting placentitis and fetal infection cause abortion, often in the last trimester. The exact mechanism is not fully understood, but likely involves endotoxin production and inflammatory damage.

- **FHV-1**: After primary respiratory infection, the virus replicates in the upper respiratory tract and conjunctiva, causing viremia. During pregnancy, the virus can cross the placenta, infecting the fetus. Fetal infection leads to necrosis in multiple organs, particularly the liver and lungs, causing fetal death and abortion. The virus may also cause placentitis. Abortion typically occurs 1-2 weeks after primary infection, often in the first half of gestation.

- **FIP**: The mutated virus infects macrophages, leading to systemic vasculitis and granulomatous inflammation. In pregnant queens, the severe systemic illness causes fever, anorexia, and organ failure, which can compromise the pregnancy. The virus may also directly infect the placenta, causing placentitis and fetal death. Abortion is often a consequence of maternal debilitation rather than direct fetal infection.

- **Toxoplasma gondii**: After ingestion, the parasite invades the intestinal epithelium, then disseminates as tachyzoites via the bloodstream and lymphatics. During pregnancy, tachyzoites cross the placenta and infect the fetus, causing necrosis in the brain, liver, and other organs. The severity of fetal disease depends on the stage of pregnancy; early infection may cause resorption, while later infection may cause abortion or stillbirth. The parasite also causes placentitis, further compromising fetal viability.

Several factors increase the risk of infectious abortion:

- **Intrinsic factors**: - Age: Young, primiparous animals are more susceptible to primary infections (e.g., FHV-1, Toxoplasma). - Breed: Purebred cats (e.g., Persians, Siamese) may have higher susceptibility to FIP. Certain dog breeds may have genetic predispositions to immune dysfunction. - Parity: Primiparous females are at higher risk for abortion due to lack of prior immunity. - Immunosuppression: Concurrent diseases, stress, or corticosteroid therapy can reactivate latent infections (e.g., FHV-1) or increase susceptibility to opportunistic pathogens. - Nutritional status: Malnutrition can impair immune function.

- **Extrinsic factors**: - Breeding management: Poor hygiene in kennels/catteries, overcrowding, and introduction of new animals can facilitate transmission. - Stress: Transportation, changes in environment, or social stress can trigger reactivation of latent infections. - Exposure to infected animals: Contact with aborted fetuses, placentas, or vaginal discharges is a major risk. - Zoonotic transmission: Humans can carry Brucella or Campylobacter on clothing or hands, potentially infecting animals. - Vaccination status: Incomplete vaccination against FHV-1 may increase susceptibility. - Outdoor access: Increases exposure to Toxoplasma oocysts and other pathogens.

Clinical signs vary depending on the agent and stage of pregnancy:

- **Brucella canis**: Abortion typically occurs between days 45-59 of gestation. There may be a serosanguineous to mucopurulent vaginal discharge for 1-6 weeks after abortion. Some dogs may have no systemic signs, but others may show lethargy, fever, and lymphadenopathy. In males, epididymitis, scrotal dermatitis, and infertility may be observed. The bitch may have a prolonged interestrus interval or fail to conceive.

- **Campylobacter**: Abortion is often preceded by mild diarrhea, but may be asymptomatic. The abortion occurs in the last trimester, with expulsion of autolyzed fetuses. There may be a purulent vaginal discharge.

- **FHV-1**: Abortion occurs 1-2 weeks after primary respiratory infection. The queen may show sneezing, nasal discharge, conjunctivitis, and fever. Abortion may be the only sign in some cases, especially in subclinical infections. Fetuses are often autolyzed.

- **FIP**: Abortion is a rare manifestation. The queen may show signs of systemic illness: fever, weight loss, icterus, ascites, or dyspnea (effusive form) or neurological signs (non-effusive form). Abortion may occur as a consequence of severe disease.

- **Toxoplasma gondii**: Abortion may occur without prior clinical signs, or the queen may show fever, lethargy, and anorexia. In some cases, there may be ocular or neurological signs. The abortion typically occurs in the second half of gestation.

Differential diagnoses for infectious abortion include:

1. **Non-infectious causes**: - **Progesterone deficiency**: Luteal insufficiency leading to embryonic resorption or abortion. Diagnosis: serum progesterone <2 ng/mL. - **Hypothyroidism**: Can cause infertility and abortion. Diagnosis: low T4, high TSH. - **Uterine pathology**: Cystic endometrial hyperplasia, pyometra, or uterine torsion. - **Trauma**: Abdominal trauma can cause fetal death. - **Genetic abnormalities**: Chromosomal anomalies in fetuses. - **Nutritional deficiencies**: Vitamin A or E deficiency.

2. **Other infectious causes**: - **Canine herpesvirus-1 (CHV-1)**: Causes abortion in dogs, especially in young puppies. Diagnosis: PCR on fetal tissues. - **Canine distemper virus**: Can cause abortion in dogs. - **Feline leukemia virus (FeLV)**: Can cause abortion in cats. - **Feline immunodeficiency virus (FIV)**: May cause abortion. - **Bacterial infections**: E. coli, Streptococcus, Staphylococcus, Mycoplasma, Chlamydia. - **Protozoal infections**: Neospora caninum, Besnoitia.

3. **Endocrine disorders**: Diabetes mellitus, hyperadrenocorticism.

4. **Iatrogenic**: Administration of abortifacient drugs (e.g., prostaglandins, glucocorticoids).

5. **Idiopathic**: Unknown cause.

A systematic approach to diagnose infectious abortion includes:

1. **History and clinical examination**: Obtain a thorough history of breeding dates, vaccination status, exposure to other animals, and any previous abortions. Perform a complete physical examination, including vaginal inspection and palpation.

2. **Vaginal cytology**: Collect a swab from the cranial vagina for cytology. In abortion, there may be neutrophils, bacteria, and cellular debris. Cytology can help rule out other causes of discharge.

3. **Hematology and biochemistry**: Complete blood count (CBC) may show leukocytosis or leukopenia. Serum biochemistry may reveal hyperglobulinemia (in FIP) or elevated liver enzymes.

4. **Serology**: - **Brucella canis**: Rapid slide agglutination test (RSAT) or tube agglutination test (TAT) for screening; confirm with agar gel immunodiffusion (AGID) or ELISA. A positive result indicates exposure. - **FHV-1**: Serology is not diagnostic due to high seroprevalence; paired titers may show a 4-fold rise. - **FIP**: Serology for coronavirus antibodies is not specific; diagnosis is based on histopathology and immunohistochemistry. - **Toxoplasma**: IgM and IgG titers. A 4-fold rise in IgG or presence of IgM indicates recent infection.

5. **Molecular diagnostics**: PCR on blood, vaginal swabs, fetal tissues, or placenta for Brucella, Campylobacter, FHV-1, FIP, and Toxoplasma. PCR is highly sensitive and specific.

6. **Ultrasonography**: Assess fetal viability, fetal heart rate, and placental appearance. Fetal death is indicated by absence of heartbeat, loss of fetal movement, and changes in fetal fluid echogenicity.

7. **Radiography**: May show fetal skeletal mineralization (after day 42-45) and fetal count. Fetal death may be indicated by overlapping skull bones (Spalding sign) or gas in the uterus.

8. **Pathology**: If abortion occurs, submit aborted fetuses, placenta, and uterine discharge for culture, PCR, and histopathology. Necropsy may reveal characteristic lesions.

9. **Culture**: Aerobic and anaerobic bacterial culture of vaginal swabs, fetal stomach contents, and placenta. Brucella requires special media (e.g., Brucella agar) and prolonged incubation.

10. **Zoonotic precautions**: Handle all samples with gloves, as Brucella and Toxoplasma are zoonotic.

Laboratory findings vary by agent:

- **Brucella canis**: - Hematology: Mild anemia, lymphocytosis, or monocytosis. - Biochemistry: Hyperglobulinemia (due to chronic infection). - Serology: Positive RSAT/TAT, confirmed by AGID or ELISA. - Culture: Isolation from blood, vaginal discharge, or fetal tissues. - PCR: Positive on blood or tissues.

- **Campylobacter**: - Fecal culture: Positive for Campylobacter spp. - PCR: Positive on fecal or tissue samples. - Hematology: May be normal or show mild leukocytosis.

- **FHV-1**: - PCR: Positive on conjunctival, nasal, or oropharyngeal swabs, or fetal tissues. - Virus isolation: Possible but less sensitive. - Serology: Paired titers may show a 4-fold rise. - Hematology: May show lymphopenia.

- **FIP**: - Hematology: Lymphopenia, neutrophilia, anemia. - Biochemistry: Hyperglobulinemia, hypoalbuminemia, elevated liver enzymes. - Rivalta test: Positive on effusion fluid. - PCR: Positive for coronavirus in effusion or tissues. - Histopathology: Pyogranulomatous inflammation with positive immunohistochemistry.

- **Toxoplasma gondii**: - Serology: Positive IgM (recent infection) or 4-fold rise in IgG. - PCR: Positive on blood, fetal tissues, or placenta. - Histopathology: Tachyzoites or cysts in tissues. - Hematology: May be normal.

Imaging findings in infectious abortion:

- **Ultrasonography**: - Early pregnancy: May show embryonic resorption (loss of heartbeat, disorganized fetal structures). - Late pregnancy: Fetal death is indicated by absence of heartbeat, fetal movement, and loss of fetal fluid. The fetal heart rate may be <160 bpm (normal >200 bpm). The placenta may appear thickened or hyperechoic. Uterine fluid may be echogenic due to inflammation. - Fetal measurements: Biparietal diameter (BPD) can estimate gestational age; a discrepancy may indicate fetal growth retardation.

- **Radiography**: - After day 42-45, fetal skeletons are visible. Fetal death may be indicated by overlapping skull bones (Spalding sign), gas in the uterus, or fetal collapse. - Radiography is less sensitive than ultrasound for fetal viability.

- **CT/MRI**: Not routinely used, but may be helpful in cases of suspected uterine torsion or neoplasia.

- **Vaginoscopy**: May reveal vaginal discharge, but is not diagnostic for infectious abortion.

Cytological and histopathological findings:

- **Vaginal cytology**: In abortion, there may be neutrophils, macrophages, and cellular debris. The presence of bacteria may be noted, but is not specific.

- **Fetal and placental histopathology**: - **Brucella canis**: Placentitis with necrosis, mononuclear cell infiltration, and intracytoplasmic bacteria in trophoblasts. Fetal tissues may show bronchopneumonia, myocarditis, and hepatitis. - **Campylobacter**: Placentitis with suppurative inflammation and necrosis. - **FHV-1**: Focal hepatic necrosis, intranuclear inclusion bodies in hepatocytes and trophoblasts. - **FIP**: Pyogranulomatous vasculitis and perivascular cuffing in multiple organs. - **Toxoplasma**: Necrotizing encephalitis, myocarditis, and hepatitis with tachyzoites and tissue cysts.

- **Special stains**: Gram stain for bacteria, immunohistochemistry for FHV-1 and FIP, and Giemsa or Wright stain for Toxoplasma.

Treatment strategies depend on the causative agent and the stage of pregnancy:

- **Brucella canis**: - **Antibiotic therapy**: Long-term combination therapy is recommended, but cure is difficult. Common protocols include: - Minocycline (10 mg/kg PO q12h) or Doxycycline (5-10 mg/kg PO q12h) for 4 weeks, combined with Streptomycin (10 mg/kg IM q24h) for the first 2 weeks, or Gentamicin (6-8 mg/kg SC/IM q24h) for the first 7-10 days. - Alternative: Enrofloxacin (5-10 mg/kg PO q24h) for 4 weeks, combined with Doxycycline. - **Ovariohysterectomy**: Recommended to eliminate the source of infection and prevent shedding. - **Zoonotic precautions**: Inform owners of the zoonotic risk.

- **Campylobacter**: - **Antibiotics**: Erythromycin (10-20 mg/kg PO q8h) or Azithromycin (5-10 mg/kg PO q24h) for 5-7 days. Supportive care for diarrhea.

- **FHV-1**: - **Antiviral therapy**: Famciclovir (40-90 mg/kg PO q8h) for 7-14 days. Lysine (250-500 mg PO q12h) may reduce viral replication. - **Supportive care**: Fluids, nutritional support, and eye care if conjunctivitis. - **Vaccination**: Vaccinate queens before breeding to reduce the risk of primary infection.

- **FIP**: - **No effective treatment**: Supportive care with corticosteroids (e.g., prednisolone 1-2 mg/kg PO q24h) may temporarily improve clinical signs. Newer antiviral drugs (e.g., GS-441524) are promising but not widely available. - **Euthanasia**: Often recommended due to poor prognosis.

- **Toxoplasma gondii**: - **Antiprotozoal therapy**: Clindamycin (10-12 mg/kg PO q12h) or Sulfadiazine/Trimethoprim (15 mg/kg PO q12h) for 2-4 weeks. Pyrimethamine (0.5-1 mg/kg PO q24h) combined with sulfonamides. - **Supportive care**: Fluids and nutritional support.

- **General management**: - **Termination of pregnancy**: If abortion is inevitable or the dam is severely ill, consider ovariohysterectomy or induction of abortion with prostaglandins (e.g., dinoprost 0.1-0.25 mg/kg SC q8-12h) and/or cabergoline (5 mcg/kg PO q24h). - **Isolation**: Isolate the affected animal to prevent spread. - **Disinfection**: Clean and disinfect the environment with appropriate agents (e.g., bleach for Brucella, accelerated hydrogen peroxide for FHV-1).

Prognosis varies:

- **Brucella canis**: Poor for future fertility; chronic infection persists. With aggressive antibiotic therapy, some dogs may clear the infection, but relapse is common. Ovariohysterectomy is curative for the bitch, but the zoonotic risk remains.

- **Campylobacter**: Good with appropriate antibiotic therapy; abortion is usually a one-time event.

- **FHV-1**: Good for the queen's life, but abortion may recur if reactivation occurs. Future pregnancies may be normal if the queen is vaccinated and stress is minimized.

- **FIP**: Grave; most cats die within weeks to months. Abortion is a minor concern compared to systemic disease.

- **Toxoplasma**: Good for the queen; abortion is usually a one-time event. Future pregnancies are typically normal.

Follow-up care includes:

- **Serial ultrasonography**: Monitor fetal viability and uterine involution after abortion. - **Serology**: Repeat titers for Brucella (every 3-6 months) to monitor treatment response. - **Vaginal cytology**: Monitor for resolution of infection. - **Breeding management**: Delay breeding until the infection is resolved. For Brucella, consider culling infected animals. - **Zoonotic precautions**: Educate owners about hygiene and risks. - **Vaccination**: Ensure vaccinations are up to date for FHV-1 and other pathogens.

**Pearls**: - Always consider Brucella canis in any dog with abortion, especially in breeding kennels. - Fetal heart rate <160 bpm indicates fetal distress; <140 bpm is critical. - In cats, FHV-1 abortion is often preceded by upper respiratory signs; vaccinate queens before breeding. - Toxoplasma abortion is rare; consider it in cats with outdoor access. - Use PCR for definitive diagnosis of infectious agents.

**Pitfalls**: - Do not use corticosteroids in pregnant animals unless absolutely necessary, as they can cause abortion. - Avoid using enrofloxacin in young dogs due to cartilage damage. - Do not administer oxytocin for abortion unless the cervix is open and the fetus is in the birth canal. - Do not rely solely on serology for FHV-1 or FIP diagnosis; PCR and histopathology are more accurate. - Always handle aborted materials with gloves to prevent zoonotic infection.

Detailed drug protocols based on Plumb's Veterinary Drug Handbook:

- **Brucella canis**: - Minocycline: 10 mg/kg PO q12h for 4 weeks. - Doxycycline: 5-10 mg/kg PO q12h for 4 weeks. - Streptomycin: 10 mg/kg IM q24h for 2 weeks (combined with minocycline). - Gentamicin: 6-8 mg/kg SC/IM q24h for 7-10 days (alternative). - Enrofloxacin: 5-10 mg/kg PO q24h for 4 weeks (combined with doxycycline).

- **Campylobacter**: - Erythromycin: 10-20 mg/kg PO q8h for 5-7 days. - Azithromycin: 5-10 mg/kg PO q24h for 5-7 days.

- **FHV-1**: - Famciclovir: 40-90 mg/kg PO q8h for 7-14 days. - Lysine: 250-500 mg PO q12h.

- **FIP**: - Prednisolone: 1-2 mg/kg PO q24h. - GS-441524: 4-10 mg/kg SC q24h (investigational).

- **Toxoplasma**: - Clindamycin: 10-12 mg/kg PO q12h for 2-4 weeks. - Sulfadiazine/Trimethoprim: 15 mg/kg PO q12h for 2-4 weeks. - Pyrimethamine: 0.5-1 mg/kg PO q24h (combined with sulfonamides).

- **Abortion induction**: - Dinoprost (PGF2α): 0.1-0.25 mg/kg SC q8-12h. - Cloprostenol: 1-2 mcg/kg SC q48h. - Cabergoline: 5 mcg/kg PO q24h. - Oxytocin: 0.5-2 IU/kg IM (only if cervix is open).

Key literature and consensus guidelines:

- **Brucella canis**: Studies by Carmichael and Shin (1996) and Hollett (2006) established the efficacy of combination antibiotic therapy. The American College of Theriogenologists (ACT) recommends ovariohysterectomy as the most effective treatment to eliminate shedding.

- **Campylobacter**: Research by Fox (2006) highlights the zoonotic potential and the need for hygiene in kennels.

- **FHV-1**: Studies by Gaskell and Dawson (2001) and Thiry et al. (2009) support the use of famciclovir and vaccination to reduce abortion risk.

- **FIP**: The FIP consensus guidelines (2018) from the European Advisory Board on Cat Diseases (ABCD) recommend supportive care and consider antiviral therapy experimental.

- **Toxoplasma**: The ABCD guidelines (2016) recommend clindamycin for treatment and emphasize the importance of preventing exposure in pregnant queens.

- **General**: The BSAVA Manual of Canine and Feline Reproduction and Neonatology (2018) provides comprehensive protocols for managing infectious abortion. The ACT and ECAR guidelines stress the importance of biosecurity and zoonotic precautions.