Bovine Genital Campylobacteriosis

Bovine genital campylobacteriosis is caused by either Campylobacter fetus venerealis or C fetus fetus, which are motile, gram-negative, curved or spiral, polar flagellated, microaerophilic bacteria. For years, C fetus fetus was thought to be mainly an intestinal organism that only occasionally caused abortion in cattle and did not cause infertility. However, C fetus fetus is now known to be a considerable cause of the common infertility syndrome usually attributed to C fetus venerealis. Several strains of C fetus fetus exist, and the only way to determine whether a strain is a cause of infertility is to test a potentially infected group of heifers.

Campylobacter spp are very labile and are destroyed quickly by heating, drying, and environmental exposure. Unless cultured quickly after collection from the animal and grown under microaerophilic or anaerobic conditions, Campylobacter spp will not grow.

C fetus is transmitted venereally and also by contaminated instruments or bedding, or by artificial insemination with contaminated semen. Individual bulls vary in their susceptibility to infection; some become permanent carriers, whereas others appear to be resistant to infection. The primary factor associated with this variability is likely to be the age-related depth of the preputial and penile epithelial crypts.

In young bulls (< 3–4 years old), whose crypts have not yet developed, infection tends to be transient; transmission relies on sexual contact with a noninfected cow minutes to days after the young bull is bred with an infected cow. Spontaneous clearance in younger bulls is not related to any immune response; therefore, reinfection can readily occur. In older bulls (> 3–4 years old), deeper crypts may provide the proper microaerophilic environment required for chronic infections to establish.

In cows, the duration of the carrier state is also variable; some cows clear the infection rapidly, whereas others can carry C fetus for ≥ 2 years. IgA is shed in cervical mucus in substantial amounts in approximately 50% of cows for several months after infection and is useful diagnostically. Although most of the genital tract may be free of infection when a cow eventually conceives, the vagina can remain chronically infected through pregnancy.

Cows with bovine genital campylobacteriosis are systemically normal; however, mucopurulent endometritis of varying extent can cause early embryonic death, prolonged luteal phases, irregular estrous cycles, repeat breeding, and, consequently, protracted calving periods, assuming the breeding season is long enough to allow for complete clearance and successful rebreeding. Observed abortions are not common.

In herds not managed intensively, disease may be noticed only when pregnancy examinations reveal low or marginally low pregnancy rates. In particular, substantial variation in gestation length within a naturally bred herd is suggestive of genital campylobacteriosis, especially when the disease has recently been introduced to the herd. In subsequent years, infertility is usually confined to replacement heifers and a few susceptible cows. Bulls are clinically healthy and produce normal semen.

• Vaginal mucus agglutination test (multiple cows)

• ELISA

• Immunofluorescence assay

• Culture

Campylobacteriosis and trichomoniasis are similar syndromes in cattle, and diagnostic investigations should be directed at both diseases. Systemic antibody responses are not diagnostically helpful, because they are often due to nonpathogenic Campylobacter spp. A vaginal mucus agglutination test (VMAT) is useful; however, because of variability in individual responses, at least 10% of the herd or at least 10 cows should be sampled. An ELISA has been developed for use on vaginal mucus and is considered to be more sensitive and better able to detect a wider range of antibody responses than the VMAT. A PCR assay is also available but may be too costly for screening and should be reserved for final confirmation of the diagnosis. Vaginal culture immediately after abortion or infection can facilitate diagnosis, but the number of organisms may be low; in addition, because C fetus is labile and requires special techniques for isolation, successful culture is limited.

An accurate diagnostic method is to intentionally breed heifers to examine them for infection; however, this is seldom practical. More often, the preputial cavity and fornix of bulls are either scraped and aspirated with an infusion pipette or infused with a buffered sterile saline solution, and the prepuce is massaged vigorously in the area of the fornix. The aspirate or sheath washing is then examined using an immunofluorescence assay and culture. C fetus survives for only 6–8 hours after collection; however, inoculation into Cary-Blair or Weybridge or similar transport media allows it to survive for > 48 hours. For maximum accuracy, bulls should be sampled twice, approximately 1 week apart.

Caution should be exercised when isolating Campylobacter spp from the placenta because of possible contamination by nonpathogenic fecal Campylobacter spp. Conversely, failure to successfully isolate C fetus from an infected aborted fetus or placenta often results from overgrowth of the colonies by contaminating organisms or from the lethal effects of atmospheric oxygen.

• Vaccination

• Antimicrobial administration in bulls (only as permitted)

Vaccination should start as soon as bovine genital campylobacteriosis is diagnosed. Infected cows and cows at risk should be vaccinated. Vaccinating infected cows hastens the elimination of C fetus, and although cows can remain carriers, fertility is greatly improved. In routine use, the vaccine should be administered once, approximately 4 weeks before breeding starts. Because antibody responses are short-lived, cows should be revaccinated halfway through the breeding season. Bulls are vaccinated for the same reason as cows (ie, for treatment as well as for prophylaxis) but are given twice the volume of vaccine per dose as cows, and the dose is repeated 3 weeks later.

Historically, treatments for infection in bulls included 2 doses of streptomycin at 20 mg/kg, SC, on consecutive days, together with 5 g of streptomycin in an oil-based suspension applied to the penis for 3 consecutive days. However, because of current concerns about aminoglycoside use in both food animals and food-producing animals, efforts should instead focus mainly on practical efforts to minimize risk of transmission (eg, vaccination, artificial insemination).

If systemic treatment is pursued, drug selection should be based on the results of an antimicrobial susceptibility panel. Any local regulations regarding antimicrobial use in food animals must be observed, including associated withdrawal times. Regulations for topical antimicrobials applied to bulls must also be observed. Herd management may require culling of infected bulls.

For practical reasons, cows are not usually treated for genital campylobacteriosis. When practical, artificial insemination is an excellent way to prevent or control the disease. Because C fetus has been isolated from cows at > 6 months after the end of pregnancy, it has been suggested that artificial insemination should continue until all cows in a herd have been through at least two pregnancies.

• Monke HJ, Love BC, Wittum TE, Monke DR, Byrum BA. Effect of transport enrichment medium, transport time, and growth medium on the detection of Campylobacter fetus subsp. venerealis. J Vet Diagn Invest. 2002;14(1):35-39.

• Peter D. Bovine venereal diseases. In: Youngquist RS, ed. Current Therapy in Large Animal Theriogenology. Saunders; 1997:355-363.

• Yaeger MJ, Holler LD. Bacterial causes of bovine infertility and abortion. In: Youngquist RS, Threlfall WR, eds. Current Therapy in Large Animal Theriogenology. 2nd ed. Saunders; 2007:389-399.