This article is from the Fall 1998 AFRMA Rat & Mouse Tales news-magazine.

By Carmen Jane Booth, D.V.M.

Q When rats abort or absorb the litter at 2 weeks gestation, is this caused by a bacteria, virus, or something else?

A The abortions could be caused by any number of things including bacteria, fungi, microscopic parasites, viruses, nutritional problems, and environmental factors.

What do the dead pups look like? This is key. If they are very smelly and look rotten, then it is probably a bacterial infection. If they look pretty normal, just immature, than virus, nutritional, or environmental factors would be more likely than bacteria.

How are the moms? Do they have a bad smelling vaginal discharge? If they do, what color is it?

What I would suggest is that if these females are rebred, that the following be implemented:

1. Make sure that the environment is as stress free as possible, i.e., no drafts, but good ventilation. Keep the cages clean with fresh bedding. What type of bedding is being used? Feed good quality rodent blocks and no fresh food (avoid any potential food born bacterial problems). Provide clean fresh water (not tap, get bottled) every 3 days if using bottles. Keep the environmental noises to a minimum.
2. Once they look pregnant, around day 15–17 post breeding, do not disturb them other than to a provide food and water. I would change the cage one more time, with lots of bedding and nesting material and then leave them alone except for food and water until they deliver.
3. If they abort, immediately put all the dead pups in a clean plastic container and try not to touch them with your hands. I would use gloves or clean tongs. This might sound strange, but you do not want to contaminate them with the normal bacteria on your skin. I would take them to the vet and have some of them cultured for bacteria (external, placental, and liver and lung if the vet can find them) and have some or all the bodies submitted for histopathology.

What is really needed for viruses is to have a blood sample tested from the mom. Most veterinarians cannot get a sample from the tail vein of a rat. It only takes 300 microliters of serum (½–1 cc whole blood) to do a full viral profile.

I would also do a vaginal smear to look for bacteria, microscopic parasites, and bacterial culture on the mom. Getting some of the small placentas cultured and submitted for histopathology is also very important. In other animal species, we can frequently diagnose the most likely cause by looking at the placenta.