Abortion in cattle • Definition • Incidence • Diagnosis • Causes • Prevention

Definition of abortion in cows Abortion in the cow is defined as foetal death and expulsion between day 45 and day 265 of pregnancy.

Incidence Most cattle herds suffer an abortion rate of 1-2%. A single abortion, is thus no great cause for alarm.

• An annual abortion rate up to 5% is considered to be normal. This figure excludes most abortions occurring during the second and third month of gestation as these often go undetected.

• An abortion rate in excess of 10% is considered an abortion storm.

Diagnosis The diagnosis of the cause of abortion is difficult and in only 20-30% of cases is a diagnosis made.

Samples for diagnosis of abortion in cows Efforts should be made to collect the complete fetoplacental unit and a sample of maternal serum.

The placenta and foetus should be cleaned with water or saline, and chilled.

It is best to submit the whole calf and placenta to the laboratory for diagnosis. It is often more convenient to perform the post mortem examination on the farm and collect only selected organ/tissue samples for further laboratory examination.

Samples submitted to the lab should include these organs or sections of them:

• stomach or abomasal contents • heart blood or fluid from a body cavity • lung • liver • kidney • spleen • brain (especially in case of neosporosis suspicion) • skeletal muscle • placenta

Abortion caused by phytotoxins Abortion may be caused by toxins (poisons) found in plants such as:

• Ponderosa pine needles • Locoweed • Broom snakeweed (Gutierrezia) • Moldy sweet clover

Locoweed (Oxytropis or Astragalus sp) contains an indolizidine alkaloid that can affect the corpus luteum, chorioallantois, and neurons, resulting in abortion or deformities.

Broomweed (Guttierrezia microcephala) ingestion can also cause abortion, as can coumarins from rat poison, many grasses, or moldy sweet clover.

Abortion caused by mycotoxins Mycotic (caused by mycotoxins) abortions may be seen in increased numbers in spring, due to cattle consuming moldy feed contaminated with mycotoxins. These abortions are typically sporadic and occur from four months to term. Severe infection of the placenta will be seen, characterized by a leathery thickening of the areas in between the cotyledons. In about 25 per cent of the cases, the fungus invades the foetus, and red or white ring-worm-like lesions can be seen in the foetal skin.

Causes of abortion 1. Non-infectious causes

- genetic - environmental: temperature - nutritional: phytotoxins including mycotoxins - iatrogenic: administration of abortifacient drugs

2. Infectious causes - general infections with high fever - specific infections such as brucellosis, BVD etc.

Infectious causes of abortion Infectious factor Common names

Abortion rate

Abortion timing

Recurrence of abortion Foetal lesions Samples

Bacterial

Brucella abortus

Brucellosis

Bang’s disease

Zoonosis

Up to 80% of unvaccinated animals infected in 1st or 2nd trimester

6-9 months

Abortion or stillbirth 2 wk to 5 mo after infection

Majority abort only once

Placenta: retained, cotyledons necrotic, red-yellow,; area between thickened

Calf: normal or autolytic with bronchopneumonia

placenta, foetus, or uterine discharge

Diagnosis: maternal serology, IFAT for Abs in placenta, bacteria isolation

Campylobacter fetus venerealis

Vibriosis

>10% 5-8 months

Uncommon, convalescent cows resistant to infection

Placenta: mild placentitis, hemorrhagic cotyledons and an edematous intercotyledonary area.

Placenta, foetal abomasal contents, vaginal flushing

Diagnosis: microscopic detection, isolation

Infectious causes of abortion Infectious factor Common names

Abortion rate

Abortion timing

Recurrence of abortion Foetal lesions Samples

Foetus: fresh or autolysed; mild fibrinous pleuritis, peritonitis, bronchopneumonia.

C fetus fetus

C jejuni Sporadic 4-9

months

Uncommon, convalescent cows resistant to infection

See above See above

Leptospira interrogans, serovarsgrippotyphosa, pomona, hardjo, canicola, icterohaemorrhagiae

Zoonosis

5-40%

Last trimester

Abortion 2-5 weeks after infection

Immunity to the serotype causing abortion but sensitive to other types

Placenta: diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areas

Foetus: autolysed

Placenta, foetus

Diagnosis: IFAT foe Abs or PCR testing forLeptospira

Arcanobacterium (Actinomyces) pyogenes

Sporadic Any stage Not known

Placenta: endometritis and diffuse placentitis, reddish brown to brown colour.

Foetus: autolysed, fibrinous pericarditis, pleuritis, or peritonitis

Placenta, foetus

Identification in bacterial culture from placenta or abomasal contents

Listeria monocytogenes

Zoonosis

Usually sporadic but can reach 50%

Last trimester May recur

Dam: fever, inappetance

Placenta: retained

Foetus: autolysed Fibrinous polyserositis and white necrotic foci in the liver and/or

Placenta, foetus

Identification in bacterial culture from placenta or abomasal contents

Infectious causes of abortion Infectious factor Common names

Abortion rate

Abortion timing

Recurrence of abortion Foetal lesions Samples

cotyledons Fungal

Aspergillus sp (60-80%

Mucor sp, Absidia, orRhizopus sp

Usually sporadic but can reach 5-10%

4 months to term

most common in winter

May recur

Placenta: severe, necrotising placentitis Cotyledons enlarged, necrotic, intercotyledonary area is thickened and leathery.

Foetus: autolysed~30% have gray ringworm-like skin lesions principally involving the head and shoulders

Foetus, placenta

Diagnosis: isolation from the stomach contents, placenta, and skin lesions.

Protozoan

Tritrichomonas (Trichomonas) foetus

Trichomoniasis

Sporadic first half of gestation

Animal gains immunity but probably not life-long

Placenta: retained, mild placentitis with hemorrhagic cotyledons and thickened intercotyledonary areas covered with flocculent exudates

Foetus: no specific lesions

Placenta, foetus, vaginal/uterine discharge

Diagnosis: detection in abomasal contents, placental fluids, and uterine discharges

Neospora caninum

Neosporosis

High in first gestation and when infection enters the naïve herd

Up to 30% first outbreak

Any stage, but most often 5-6 months

Decreases with parity but always possible

Placenta, foetus: no specific gross lesions, autolysed

Microscopic: focal encephalitis with necrosis and nonsuppurative inflammation, hepatitis in

Placenta, foetus (brain, heart, liver, body fluids), serum samples from the dam

Diagnosis: detection of antigen in brain histology samples

Immunochemistry in

Infectious causes of abortion Infectious factor Common names

Abortion rate

Abortion timing

Recurrence of abortion Foetal lesions Samples

Enzootic: 5-10%

tissue samples

Abs - PCR, ELISA Viral

Bovine Viral Diarrhoea Virus

BVD-MD

Usually low

Complex pathology

Abortion usually up to 4 months

Uncommon, immunity develops

Placenta: retained, no specific lesions

Foetus: no specific lesions, autolysed, mummified

Placenta, foetus (preferred -spleen), dam and herdmates serum

Diagnosis: isolation, immunologic staining, PCR, or detection of precolostral antibodies in aborted calves

Bovine Herpesvirus type I (BHV I)

Infectious Bovine rhinotracheitis virus (IBRV)

IBR

IBR-IPV

5-60%

in non vaccinated herds

Possibly any stage but most common

from 4 months to term

Uncommon, immunity develops

In the majority of cases there are no gross lesions in the placenta or foetus

Placenta: necrotizing vasculitis

Foetus: autolysed, foci of necrosis in the liver

Placenta, foetus, serum samples from the dam

Diagnosis: Immunochemistry in samples from kidney and adrenal glands, blood serology, PCR

Blue tongue virus

Blue tongue Usually low Variable Unlikely

No specific

Foetus: autolysed

Placenta, foetus, serum samples from the dam

Diagnosis: virus isolation

Epizootic Bovine Abortion

Foothill Abortion

etiologic agent has not been definitively

Can reach 75%

Limited mainly to California in the US

Usually in the last trimester

Unlikely

Placenta: No specific

Foetus: hepatomegaly, splenomegaly, and generalized

Anamnesis

Diagnosis: elevated foetal Ig-G

Infectious causes of abortion Infectious factor Common names

Abortion rate

Abortion timing

Recurrence of abortion Foetal lesions Samples

determined,

vector – tickOrnithodoros coriaceus

lymphomegaly. Microscopically - marked lymphoid hyperplasia in the spleen and lymph nodes and granulomatous inflammation in most organs.

Factors not typical for cattle or rarely occurring

Chlamydophila abortus (Chlamydia psittaciserotype 1)

enzootic abortion of ewes

Zoonosis

Sporadic

Near the end of the last trimester

Unlikely

Placenta: placentitis, thickening and yellow-brown exudate adhered to the cotyledons and intercotyledonary areas. Foetus: fresh, minimal autolysis, pneumonia, hepatitis

Placenta, foetus Diagnosis: identification in stained smears of the placenta or by ELISA, fluorescent antibody staining, PCR, or isolation in embryonated chicken eggs or cell culture.

Ureaplasma diversum

Usually sporadic, but outbreaks possible

Third trimester Possible

Placenta: retained, intercotyledonary areas thickened, nonsuppurative placentitis

Foetus: no gross lesions, pneumonia

Placenta, foetus

Diagnosis: isolation from the placenta, lungs, and/or abomasal contents

Salmonella spp

Usually sporadic but can take form of an abortion storm

Any stage Possible

Cows: clinically ill

Placenta and foetus: autolysed and emphysematous.

Placenta, foetus

Diagnosis: isolation from the abomasal contents other tissues.

Prevention of abortions 1. Proper hygienic and biosecurity measures in the cow's environment and feed storage 2. Isolation of aborting cows and immediate removal of aborted materials

3. Systematic evaluation of the feed for mycotoxins and other phytotoxins 4. Adequate immunization against infectious diseases causing abortion 5. Maintenance of adequate breeding and treatment records to avoid insemination of

pregnant cows and administration of drugs that may cause abortion to pregnant cows.

Prepared By:

Muhammad Farrukh Hafeez

Farrukh097@gmail.com