Strep Zooepidemicus in Dogs

Last reviewed: February 17, 2022 by Marty Greer, Doctor of Veterinary Medicine

They are classic signs no one wants to see. A pregnant looking female. She may even belly down. But her litter is then either very small or none at all. One possible cause is the bacteria Streptococcus zooepidemicus also known as Strep zoo.

Infertility and Puppy Loss

This strain of bacteria has been found to cause infertility in dogs. Kennels with Strep zoo can start out displaying minor reproductive issues and then later move to infertility or embryo death. When the embryo is killed before bone development, mom reabsorbs the fetus. Some females experience minor vaginal discharge. Strep zoo can be diagnosed by vaginal culture while in heat and then using the PCR test for Strep equi subspecies zooepidemicus. It seems to be reliable.

How Strep Zoo Grows

These bacteria live in the lower reproductive tract and grow in numbers during heat cycles. In estrus is when secretions and food for bacteria increase and when the immune system is stressed. Strep numbers increase at this time and the bacteria follow semen into the uterus. The strep bacteria becomes fatal when the embryo starts to grow fast. It is not interested in the embryo when it is tiny and not growing.

Protect the Embryos

To prevent embryo loss, breed on an antibiotic such as a long-lasting penicillin every third day when they are spotting and keep them on the antibiotic until they refuse the male. Amoxicillin is also a good choice but should be given twice a day when spotting until two days after the female refuses the male. The goal is to keep the number of these bacteria low when the cervix is open during breeding. The cervix becomes closed and the mucus plug is sealed two days after the female refuses the male so it is safe to stop then. Breeding on an antibiotic for two breedings or one year will usually work this issue out of your females. Creating a protective environment for the embryos is your goal. Since these bacteria live in the lower reproductive tract, managing the issue by preventing the bacteria from following the semen into the uterus is the key. Once the mucus plug is in, antibiotics can't help.

Want help treating and preventing Strep zoo? Call our Pet Care Pros at 800.786.4751. They have the experience and knowledge to help you manage and prevent pet care challenges.

-Dr. B
Donald Bramlage, Doctor of Veterinary Medicine, Former Director of Veterinary Services at Revival Animal Health

Donald Bramlage, Doctor of Veterinary Medicine, practiced veterinary medicine for 30+ years and is known for his work in managing parvovirus. He received his Doctor of Veterinary Medicine from Kansas State University in 1985. He served as Revival's Director of Veterinary Services from 2011 until his retirement in 2019.

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