Uterine Infections in Dairy Cattle

Adapted by Patricia Blanchard, DVM, PhD, California Animal Health and Food Safety Laboratory

In the past 6 months, the California Animal Health and Food Safety Laboratory (CAHFS) has been validating a rapid test (PCR) to detect bovine herpesvirus- 4 (BHV-4) in cattle. Validation of a new test requires testing at least 30 positive and 30 negative diagnostic submissions from different animals and confirming by another method whether the virus is truly present or not. For this virus, validation testing has been performed on uterine fluids from cows with uterine infections that were collected by a veterinarian during a herd check or by CAHFS during a necropsy at the laboratory.  BHV-4 is not considered a primary cause of uterine infections and the virus can also be carried by healthy animals. However, stress, corticosteroid use and inflammation from bacterial uterine infections activate the virus to replicate, leading to more severe damage of the endometrium. This co-infection of the uterus by various bacteria and BHV-4 causes more severe uterine infections that are less responsive to treatment. 

All uterine infections with BHV-4 detected at CAHFS also had several types of bacteria that are commonly found in cases of metritis. The more severe cases also had large numbers of mixed anaerobic bacteria. Four herds reported an increased frequency and/or severity of postpartum metritis with some deaths in first calf heifers. In these herds, BHV-4 was found in uterine fluids of some affected heifers and we also tested for other viruses that could damage the uterus directly such as Bovine herpesvirus-1 (BHV-1 aka Infectious Bovine Rhinotracheitis (IBR)) or suppress the immune response such as Bovine viral diarrhea virus (BVDV). In one herd, co-infections with BHV-4 and BHV-1 (IBR) were detected in the uterine fluid and on two dairies, co-infections with BHV-4 and BVDV were found.  BVDV was also found causing vessel damage in multiple organs and laryngitis in several heifers without BHV-4 virus in their uterus from one of the co-infected BVDV and BHV-4 dairies.  

Though vaccines for BHV-4 are not available, a good vaccine program for BVDV and IBR can prevent postpartum heifer infections with these two viruses. BVDV and IBR infections among lactating cows are most often commonly seen in first calf heifers within the first 2 weeks of freshening.  BVDV infection at this age may result in scruffy skin, diarrhea, straining to defecate, metritis, laryngitis, pneumonia, poor doing animals and rarely oral ulcers. IBR results in pneumonia and rhinotracheitis as well as vulvovaginitis with bright red vaginal mucosa that has small vesicles that rupture and form ulcers. IBR and BVDV in postpartum heifers is probably due to a combination of inadequate vaccination, ideally pre-breeding, and, in the case of BVDV, lack of exposure to the strains circulating in the cow herd. Gaps in vaccine programs for first calf heifers occur when BVDV vaccination is only given at dry off and postpartum check and to calves less than 8 months of age when maternal antibodies from colostrum may prevent good vaccine-induced immunity.

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