Abortions and stillbirths in cattle Flashcards
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
A. Abortions caused by infectious diseases usually occur after the active infection.
In cattle bovine herpesvirus 1 causes…
A. Mastitis and respiratory disease
B. Fertility problems and respiratory disease
C. Diarrhea and respiratory disease
B. Fertility problems and respiratory disease
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.
A. Culling of persistently infected animals.
How is abortion defined?
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)
stillbirth in cattle includes (3)
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
Describe Registration of abortions/perinatal mortality.
- 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!
SOP in case of abortion / stillbirth problem
standard operating procedure
- Collect information/anamnesis
- Investigate aborted cows and pregnant animals
- Investigate placenta and fetus
Describe step 1. of the standard operating procedure in the event of abortion / stillbirth problems on farms.
- 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
Describe step 2. of the standard operating procedure in the event of abortion / stillbirth problems on farms.
- 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.
Describe step 3. of the standard operating procedure in the event of abortion / stillbirth problems on farms.
- 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
Necropsy test selection algorithm.
Microbiology SOP in case of abortion / stillbirth problem
- 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
Serology SOP in case of abortion / stillbirth problem
- 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
Trace elements samples SOP in case of abortion / stillbirth problem.
- Iodine deficiency (goiter) – thyroid enlargement (>30g) - thyroid lump in formalin.
- Selenium deficiency - fetal liver or kidneys
Histopathology SOP in case of abortion / stillbirth problem
- 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.
Placenta SOP in case of abortion / stillbirth problem
- 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.
Sample handling SOP in case of abortion / stillbirth problem.
- 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.
Routes of fetal infection
- 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
Describe Opportunistic pathogens in relation to abortions.
- 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.
What is Ureaplasma in cattle?
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.
Name 5 Bacterial pathogens that can cause abortion in cattle.
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
Name main 2 Viral infections that can cause abortion in cattle.
Main pathogens:
* BHV-1
* BVDV
Malformations:
* Schmallenberg virus
* Bluetongue
Testing mainly with PCR for these.
Name Fungal infections that can cause abortion in cattle.
- 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.
Describe Neospora caninum in cattle.
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
