Camelidae and Cervidae Abortion Study Guide

Overview and Clinical Importance

Abortion in camelids (llamas and alpacas) and cervids (deer, elk, moose) represents a significant cause of reproductive loss and economic impact. These species have unique reproductive physiology that influences the etiology, diagnosis, and management of pregnancy loss. Camelids feature induced ovulation and epitheliochorial diffuse placentation, while cervids are susceptible to specific viral hemorrhagic diseases uncommon in domestic livestock. Understanding these species-specific factors is essential for NAVLE success.

PART I: Abortion in Camelidae (Llamas and Alpacas)

Unique Reproductive Features

South American camelids (SAC) have several unique reproductive characteristics that influence pregnancy and abortion. Unlike most domestic species, camelids are induced ovulators - ovulation occurs approximately 24-30 hours after mating, triggered by an ovulation-inducing factor (OIF/beta-NGF) in semen. The placentation is epitheliochorial, microcotyledonary diffuse (similar to equine), with the allantochorion adhering to the amniotic sac.

Key Reproductive Parameters

Infectious Causes of Abortion in Camelids

Abortion rates due to infectious diseases in camelids range from 10% to greater than 70% in some regions. The diagnosis rate for camelid abortions rarely exceeds 30% of submissions due to autolysis, insufficient samples, and limited expertise in camelid pathology.

Bacterial Causes

Protozoal Causes

Viral Causes

Non-Infectious Causes of Abortion in Camelids

Diagnostic Approach to Camelid Abortion

Complete abortion workup should include fetus, placenta, and maternal serum. Key submissions include fetal liver, lung, brain, kidney, lymph nodes, abomasal contents, and placenta for comprehensive testing.

• Fresh fetal tissues: liver, lung, kidney, brain, lymph nodes - for culture, PCR, IHC
• Formalin-fixed tissues: placenta, fetal organs - for histopathology
• Abomasal contents: for bacterial culture (Campylobacter, Listeria)
• Maternal serum: acute and convalescent for serology (Leptospira MAT, Toxoplasma, Neospora)
• PCR: BVDV, Leptospira, Chlamydia, Neospora, Toxoplasma

PART II: Abortion in Cervidae (Deer and Elk)

Overview of Cervid Reproductive Loss

Cervids (deer, elk, moose, reindeer) face unique reproductive challenges including susceptibility to hemorrhagic diseases (EHD, BTV), brucellosis (particularly in Greater Yellowstone Area populations), and chronic wasting disease (CWD) which has implications for vertical transmission. Wild cervids are more challenging to diagnose compared to farmed populations.

Epizootic Hemorrhagic Disease (EHD) and Bluetongue (BTV)

Hemorrhagic disease (HD) collectively refers to EHD and BTV infections in cervids. Both are Orbivirus infections transmitted by Culicoides biting midges. White-tailed deer are MOST susceptible, while elk show minimal clinical signs.

Brucellosis in Cervids

Brucella abortus infection in elk and bison represents a significant challenge in the Greater Yellowstone Area (GYA). The disease causes late-term abortion, retained placenta, and infertility. Brucellosis is a ZOONOTIC disease - humans can acquire infection through contact with infected tissues or consumption of unpasteurized dairy products.

Clinical Signs in Cervids: Often asymptomatic carriers; reproductive failure evidenced by abortion (usually last trimester), retained fetal membranes, weak offspring, orchitis in males, carpal bursitis (especially in reindeer)

Diagnosis: Plate agglutination test (serology); culture from placenta, milk, or fetal tissues; regulated testing programs for farmed cervids

Control: Test and removal; vaccination programs (strain RB51 in cattle); interstate movement regulations; Certified Brucellosis-Free Herd programs for farmed cervids

Other Infectious Causes of Abortion in Cervids

Chronic Wasting Disease (CWD) and Vertical Transmission

Chronic Wasting Disease (CWD) is a fatal prion disease affecting cervids. While not directly an abortifacient, recent research has demonstrated vertical (in utero) transmission from infected does to offspring. Studies found 80% of fetuses from CWD-positive muntjac deer dams were prion-positive, suggesting this route is more significant than previously believed.

Key Points for NAVLE: CWD is caused by misfolded prion proteins; affects deer, elk, moose, reindeer; no treatment or vaccine available; reportable disease; CWD Herd Certification Program required for interstate movement of farmed cervids

Exam Focus: CWD is NOT directly a cause of abortion but can be transmitted vertically (in utero). When presented with a case involving cervid herd with neurological disease and reproductive losses, consider CWD as a differential. Diagnosis requires post-mortem testing (obex, medial retropharyngeal lymph nodes).

Diagnostic Approach for Cervid Abortion

Cervid abortion diagnosis is often complicated by the wild/semi-wild nature of many populations. Submit complete fetal materials when available:

• Fresh fetal tissues: liver, lung, spleen, kidney, brain, lymph nodes
• Placenta and fetal membranes
• Maternal serum (acute and convalescent)
• For EHD/BTV: whole blood in EDTA for RT-PCR; spleen
• For Brucellosis: placenta, stomach contents, lung - culture and serology
• For CWD (if indicated): obex, medial retropharyngeal lymph nodes

Treatment and Prevention Summary