American Fancy Rat & Mouse Association

This article is from the Summer 2003 AFRMA Rat & Mouse Tales news-magazine.


Suddenly Ill Rat: Hemobartonella muris/Proteus Mirabilis

By Carmen Jane Booth, D.V.M.

Karen Robbins, Winnetka, CA
Q One of our new members had bought a rat from one of our members here and had it several weeks when suddenly the rat got very sick. They took it to the vet and this is what they found.

“By blood tests my vet found out the cause of the problem. One is called Hemobartonella muris which is a hemoparasite. The other she mentioned was Proteus mirabilis. Do you know anything about these? Our entire colony was treated by Doxycycline and Baytril for 3 weeks, twice a day. No other rats have shown any signs of illness. Cost us over $1,000. Any comments will be appreciated.”

Anything you can comment on this???

Answer from Carmen Jane Booth, D.V.M.

Hemobartonella muris

Hemobartonella infection in rodents is not very common in most colonies. H. muris is an extracellular parasite of erythrocytes and is transmitted primarily by the rodent louse species Polyplax spinulosa. Natural infections are usually without any clinical signs unless the spleen has been removed. It can be transmitted in utero.

I could not find any treatment for it other than cesarean derivation and elimination of infected animals. I would bet that the rat had a subclinical infection and it is an incidental finding.

Proteus mirabilis

Proteus mirabilis is a bacteria that can cause problems in many species if they are sick from other causes. Occasionally, they can be a primary pathogen, but not usually. My memory is that this bacteria likes moist environments and is ubiquitous.

The following comes from an article on P. mirabilis in people. “Proteus mirabilis is a motile gram-negative bacterium within the Enterobacteriaceae that undergoes dramatic morphological changes, from a single rod-shaped swimmer cell to an elongated multicellular swarmer cell, in response to growth on solid surfaces. P. mirabilis is found mainly in soil and the gastrointestinal tract. While considered a pathogenic organism in the young, P. mirabilis is an opportunistic pathogen in older individuals.

P. mirabilis is an important etiological agent of UTI, especially pyelonephritis. Target groups include young males and, infrequently, young females, individuals with structural abnormalities of the urinary tract, and the elderly. Many of the pathogenic mechanisms and factors contributing to virulence have been described; however, many questions concerning the pathogenesis of the organism still remain. What is the pathogenic potential of the organism outside the urinary tract? What fimbriae and adherence factors are expressed before infection by the organism when present in environments outside of the urinary tract? A large proportion of urea produced by the kidneys is transferred to the intestines in humans, but it still remains to be determined if Proteus plays a role in urea breakdown at this site and if urease is expressed by the organism in this environment. Although urease is inducible in P. mirabilis, the enzyme may be continuously expressed in the human host, and thus the organism may be poised for infection of the urinary tract.”

Baytril should be effective in treating it.

How old was this rat? The stress of going to a new home could have precipitated the underlying infections. I would guess that the Proteus is the real cause of illness in this rat and not the Hemobartonella. *

Updated April 7, 2014