Abortions and stillbirths in cattle

Question 1

The laboratory diagnosis of abortions is difficult because…..

A. Abortions caused by infectious diseases usually occur after the active infection.

B. Abortion is mainly caused by non-infectious factors.

C. There is no contamination of the fetus and fetal membranes by the environmental pathoge

Answer 1

A. Abortions caused by infectious diseases usually occur after the active infection.

Question 2

In cattle bovine herpesvirus 1 causes…

A. Mastitis and respiratory disease

B. Fertility problems and respiratory disease

C. Diarrhea and respiratory disease

Answer 2

B. Fertility problems and respiratory disease

Question 3

The overall concept of the eradication of the bovine viral diarrhea virus from the herd is…

A. Culling of persistently infected animals.

B. Culling of seropositive cattle.

C. Vaccination of all cattle with marker vaccine.

Answer 3

A. Culling of persistently infected animals.

Question 4

How is abortion defined?

Answer 4

embryonic death = fetal death before day 42 of gestation

abortion = fetal death between day 42 and 210 of gestation

stillbirth = fetal death from day 210 to birth (cow preg. for 283 days)

Question 5

stillbirth in cattle includes (3)

Answer 5

fetal death before parturition and after day 210 of gestation (typically infectious diseases)

fetal death during parturition (dystocia; malpositions, fetal-maternal disproportion etc.)

neonate death within 24 hours after parturition

Question 6

Describe Registration of abortions/perinatal mortality.

Answer 6

• Under-registration/mis-registration leading to “untagged calf syndrome”
• Diagnostic ‘gap’ for gestations up to 120days. Only 20-30% of abortions are seen on the farm.
• Personal threshold for registration, “farm blindness”, desire (reluctance) to send the material to the laboratory or fetus cannot be obtained. General threshold only 5-8%.
• However, all “abortion storms” start from single cases, so routine diagnostics are necessary!
• NB! The detected case is probably not the first!

Question 7

SOP in case of abortion / stillbirth problem

Answer 7

standard operating procedure

1. Collect information/anamnesis
2. Investigate aborted cows and pregnant animals
3. Investigate placenta and fetus

Question 8

Describe step 1. of the standard operating procedure in the event of abortion / stillbirth problems on farms.

Answer 8

1. Collect information/anamnesis

• The extent and nature of the problem
• Was the cow sick
• Do heifers/cows abort
• Recent changes
• Vaccinations
• Infectious disease situation
• Buying animals

Question 9

Describe step 2. of the standard operating procedure in the event of abortion / stillbirth problems on farms.

Answer 9

2. Investigate aborted and pregnant cattle
   * General health
   * BSC
   * Feeds, feeding

• Compare (n=5-10) those who aborted with those who did not – clinically, vaccination status etc.
• Aborted animals – fever, diarrhea, respiratory disease signs

SAMPLES
* Fecal samples in case of salmonellosis suspicion
* Single serological testing before testing the fetus – excluding maternal antibodies

• Paired serum samples (with 2 week interval) are not often practical – time distance between infection and fetal death and expulsion.

Question 10

Describe step 3. of the standard operating procedure in the event of abortion / stillbirth problems on farms.

Answer 10

3. Investigate placenta and fetus.
   External evaluation of fetus
   * Age of fetus (see table)
   * Preservation
   * Abnormalities

Internal evaluation of fetus
* See technique
* Prevent organ contamination

Sample collection
* Laboratory possibilities, anamnesis, fetal autolysis, cost

Question 11

Necropsy test selection algorithm.

Answer 11

Question 12

Microbiology SOP in case of abortion / stillbirth problem

Answer 12

• Abomasum content – piece of serous membrane with sterile scalpel blade into vacuum tube
• Sending tissues is better than swabbing them
• If septicemia is suspected, lung, liver, brain

Question 13

Serology SOP in case of abortion / stillbirth problem

Answer 13

• Fetal serology from the second trimester (>120 days), if the fetus is immunocompetent - antibodies indicate
  fetal infection, e.g. Neospora caninum, BVD
• Do not use as a sole test
• There is no test for many pathogens
• Examining mothers - vaccination?!
• A high titer is already achieved before the abortion - even paired serums often do not provide information.
• Favor serological profile in cohort comparison - aborting and non-aborting animals, preferably quantitative testing.
• IBR, BVD, Leptospirosis, Neospora

Question 14

Trace elements samples SOP in case of abortion / stillbirth problem.

Answer 14

• Iodine deficiency (goiter) – thyroid enlargement (>30g) - thyroid lump in formalin.
• Selenium deficiency - fetal liver or kidneys

Question 15

Histopathology SOP in case of abortion / stillbirth problem

Answer 15

• Samples of changed and normal tissues - lung, liver, thyroid gland, heart, brain
• If neospora is suspected, whole brain + placenta can be sent because those are the organs neospora will infect.

Question 16

Placenta SOP in case of abortion / stillbirth problem

Answer 16

• If it has not yet been expelled, a sample of the placenta / vaginal discharge could be taken.
• Ideally, tissue samples from three abnormal placentomas (macroscopically altered and uncontaminated).
• A normal placenta is thin, cotyledons are dark brown - assess the appearance of the placenta.

Placenta sample is especially good when suspecting fungal etiology for abortion.

Question 17

Sample handling SOP in case of abortion / stillbirth problem.

Answer 17

• If samples are not going to the laboratory on the same day; samples for bacteriology, serology and histopathology should be stored in a refrigerator (4°C) and for PCR in a freezer (-20°C).
• NB! Always communicate with the lab!
• It is often best to send the fetus with the placenta, but then the fetal dissection is not done.

Question 18

Routes of fetal infection

Answer 18

• Hematogenous spread through the placenta
• Ascending infection through the vagina, infection of the placenta through the cervix, from there to the amniotic fluid, the fetus
  swallows
• Fungal organisms can cross the placenta and colonize the fetal skin
• Damage to the placenta can cause fetal hypoxia

Question 19

Describe Opportunistic pathogens in relation to abortions.

Answer 19

• In case of 25-50% abortions. All that “find their way” into the bloodstream and can cause placentitis.

e.g. Arcanobacterium pyogenes, Bacillusspp, Escherichia coli, Histophilussomni, Pasteurella spp, Listeria spp, Staphylococcus spp, Streptococcus spp., Ureaplasma spp.

• Often opportunistic alongside viral infections
• Usually sporadic abortions
• Arcanobacterium pyogenes – purulent inflammations in the body; abscesses, foot
  diseases
• Listeria spp - in case of contaminated and poorly fermented silage
• Most often, changes are seen in the placenta
• To exclude contamination during sample handling, the laboratory must grow as a pure culture.

Question 20

What is Ureaplasma in cattle?

Answer 20

Ureaplasma spp., similar to the closely related Mycoplasma spp., are pleomorphic, microaerophilic bacteria that do not synthesize cell walls.

Of the seven named species, Ureaplasma diversum can be found in the respiratory and genital/reproductive tracts of cattle.

Can behave as opportunistic pathogens alongside viral infections causing abortions.

Question 21

Name 5 Bacterial pathogens that can cause abortion in cattle.

Answer 21

Brucella
Salmonella

Leptospira
* Not easily cultured, dark-field microscopy of fetal body fluids is also not the most sensitive
* Fluorescent antibody test from kidney tissue
* Maternal serology? For L. hardjo, the titer is low/absent at the time of abortion, better for L. pomona
* Underdiagnosed due to diagnostic challenges

Ureaplasma diversum
* A normal inhabitant of the respiratory system
* Needs special media, underdiagnosed?
* It is often accompanied by delayed conception, changes/damages in the amnion.

Campylobacter spp.
* Early embryonic death

Question 22

Name main 2 Viral infections that can cause abortion in cattle.

Answer 22

Main pathogens:
* BHV-1
* BVDV

Malformations:
* Schmallenberg virus
* Bluetongue

Testing mainly with PCR for these.

Question 23

Name Fungal infections that can cause abortion in cattle.

Answer 23

• Aspergillus fumigatus, Aspergillus spp, Absidia spp., Mucor spp., Rhizopus spp.,
  Candida spp., and many environmental species.
• Widespread in the environment, especially moldy litter, feeds.
• Hematogenous spread of gonidia to the placenta - the placenta ends up thickened,
  leathery, but the lesions are unevenly distributed.
• The mother often has placental retention, placentitis.
• Cultivation of fungi from fetal stomach contents and placenta on special media.

Question 24

Describe Neospora caninum in cattle.

Answer 24

Vertical transmission from mother to fetus, horizontal spread by eating feces contaminated with oocysts from an infected dog (final host).

• Abortions between 5-7 months of pregnancy.
• Recurrent abortions in the same female (seropositive animals).
• Also mummified fetuses, stillbirths, rarely calves born with nervous
  symptoms.
• Normal calves with precolostral antibodies.
• In infected females, antibody levels fluctuate and may fall below the
  detectable limit.
• Detection of the causative agent in the fetal brain, placenta by immunohistochemical methods.

cull infected cows

Question 25

Abortions of non-infectious etiology can include the following categories (6)

Answer 25

1. Idiopathic causes
2. Genetic anomalies
3. Metabolic / hormonal abnormality
4. Trauma
5. Poisonings
6. Feeding deficits

Question 26

1. Genetic anomalies that can cause abortion include (4)

Answer 26

• Chromosomal defects
• Gene defects
• Gene interactions
• Embryonic death, abortion

Question 27

Metabolic / hormonal abnormalities that can cause abortion include (2)

Answer 27

• Heat stress
   Affects the pregnancy of cows
   Hypotension, hypoxia and acidosis occur in the fetus
   Decreased body progesterone level and smaller corpus luteum
  The higher body temperature of the pregnant animal due to fever has
  probably effect.
• Stress (change of group, changes in feeding, treatment, general management)

Corticosteroids (dexamethasone, flumethasone)! contraindicated in pregnant animals.

Question 28

Traumas that can cause abortion include (2)

Answer 28

• Insemination during pregnancy
• Rectal examination

Question 29

Poisonings that can cause abortion include (4)

Answer 29

• Abortions and embryonic death
• Plant toxins (mycotoxins)

Spoiled forage - spoiled silage, self-heating grain, musty/moldy hay, straw, concentrates, green fodder that has become hot after mowing.

• Nitrate/Nitrite
• Rat poison

Question 30

Feeding deficiencies that can cause abortion include (4)

Answer 30

Vitamins A, E,
iron and selenium-deficient feeds - no studies though.

Spoiled forage - spoiled silage, self-heating grain, musty/moldy hay, straw, concentrates, green fodder that has become hot after mowing.

Question 31

TOD

Answer 31

Time of death (TOD)

Before sampling, clarify the time of fetal death - affects the diagnostic plan.

• PREPARTUM – fetuses that die before delivery have varying degrees of autolysis. Autolytic lesions occur within about 12 hours afterdeath in utero and worsen over time.
• INTRAPARTUM - fetuses that were alive at birth but die at birth or within an hour of birth do not show signs of autolysis and may show signs of breathing (partial lung inflation).
• POSTPARTUM – dead more than an hour after calving; there are no signs of autolysis,
  they have breathed (lung inflation, foam in the trachea) and rupture of the umbilical cord (clots in the umbilical cord).

Question 32

COD

Answer 32

Cause of death

Question 33

DNR in herd management

Answer 33

Diagnosis not reached

• Abortion occurs weeks/months after infection - the causative agent can no longer be identified.
• The fetus has not been properly examined.
• Fetuses and fetal membranes are contaminated by environmental pathogens
  prior to analysis.
• Fetus is autolyzed / samples insufficient / poor quality / mishandled.
• Do not send the placenta to the laboratory.
• Laboratories do not always have the means/opportunities to diagnose these
  causes.
• Sporadic abortions are often caused by non-infectious factors.