I was recently consulted about a disease investigation involving a group of heifers that was exposed to three bulls during a 90-day breeding season.
The bull-cow ratio was more than adequate and the heifers were well vaccinated, receiving a modified live pre-breeding vaccine, as well as being vaccinated for vibriosis (Campylobacter) and leptospirosis.
The herd veterinarian was trying to discover the cause of a higher than usual open rate in this group of heifers.
These heifers had a non-pregnancy rate of 22 percent, which was assumed to be a result of abortion or early embryonic death.
These investigations are often challenging because it is unusual to obtain an aborted fetus or placenta in instances where the abortions occurred while the animals were grazing and the abortion problem was only discovered at the time of pregnancy diagnosis.
Veterinary diagnostic laboratories often have a diagnostic success rate for abortion of about 50 percent. However, this success rate is highly dependent on the diagnostic samples that are accessible, and the lack of a fresh fetus or placenta will make this diagnostic success rate even lower.
This particular case was very typical of what veterinarians commonly face, in that the only accessible diagnostic material was blood samples from the open heifers to assess antibody levels as well as the potential of collecting diagnostic samples from bulls for the diagnosis of Trichomoniasis or Campylobacter.
In this situation, the herd veterinarian also collected vaginal swabs from the open heifers for culture.
The fact that the heifers were well vaccinated ruled out a number of potential causes of abortion such as bovine viral diarrhea virus (BVD), infectious bovine rhinotracheitis virus (IBR) and leptospirosis.
The blood samples collected from the heifers tested negative for antibodies to two important causes of abortion: Neospora caninum and leptospirosis.
Neospora is one of the most common causes of cattle abortions found by diagnostic laboratories and is caused by a microscopic parasite that is spread in feces by canine species such as dogs and coyotes and ingested in contaminated feed by cattle.
Leptospirosis is a bacterial infection that can cause abortion and in this case the heifers had been vaccinated and also did not show the high antibody titres that could be associated with recent natural infections.
In this case, the vaginal swabs from the open heifers all tested positive for a bacteria known as Ureaplasma diversum.
Ureaplasma is a bacterial infection that has been associated with reproductive diseases of cattle for years, but the evidence for its importance is somewhat controversial.
Ureaplasma can be cultured from animals that are not experiencing any abnormal reproductive events and therefore it can be difficult to assess whether it is really a cause of abortion and infertility or just a bacteria that is a potential “innocent bystander”.
Ureaplasma diversum is a bacteria that is in the same family as the Mycoplasma family of bacteria and it is a common inhabitant of the genital tract of cattle.
It was first isolated in 1969 and was first thought to not cause any disease issues. However, subsequent research, mostly in Canadian veterinary colleges in the 1970s and 1980s, suggested that Ureaplasma could be associated with failure of pregnancy at various times of gestation in cattle.
In cows, the bacteria has been associated with an inflammatory condition in the vaginal wall, which may cause reddening and the formation of granules on the vaginal wall. In some cases, there may be some vaginal discharge as well.
A recent scientific article published in the New Zealand Veterinary Journal has provided more evidence that this may be a potential cause of infertility.
This study involved dairy herds in Spain and demonstrated that almost all of the 40 herds tested had evidence of Ureaplasma infections. The authors studied five of these herds in more detail and found that 50 percent of the cows tested positive for Ureaplasma on vaginal cultures. Fifty-seven percent of the cows that tested positive had evidence of poor reproductive efficiency while only 18 percent of the negative cows had evidence of poor reproductive efficacy demonstrating an association of this vaginal infection with poorer fertility.
The involvement of this bacteria in cattle fertility remains unclear because we don’t have a lot of causal evidence that demonstrates how it causes infertility or abortion.
In addition, we can identify the bacteria in a proportion of normal animals with no reproduction problems, which creates major questions about the role the bacteria plays.
There may be different strains of the organism that cause disease we haven’t recognized, which might explain why some animals are affected adversely and others are not.
We don’t have good evidence to suggest how to effectively control this bacteria if it is a cause of infertility.
It can be carried in the reproductive tract of bulls and cows and is transmitted through mating, as well as artificial insemination.
It is a bacterial infection and therefore potentially treatable with antibiotics. Control of the disease in dairy herds using artificial insemination was often attempted by using post-breeding uterine infusions of tetracycline. This is obviously not a practical method of control in most beef cattle herds and so we are left to speculate if using injectable tetracycline would be effective.
Despite recent research, we still don’t completely understand how this bacteria causes embryonic loss and why it can be apparently present in clinically normal cattle.
I believe it could be an overlooked cause of fetal loss because it is often not considered by veterinarians when investigating abortion problems in beef herds.
The group of heifers in my recent case was well vaccinated and many of the important infectious causes of abortions could be easily ruled out.
Ureaplasma infections are certainly something to consider as a possibility in herds that are experiencing significant infertility issues or abortion problems.
If you suspect this condition exists in your herd, contact your local veterinarian. They can collect appropriate samples and send them to a laboratory to determine if Ureaplasma is present, as well as look for other common causes of abortion or fetal loss.
John Campbell is a professor in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.