Rat Typhoid

RAT TYPHOID, an infectious disease of rats. In its millennial, generally not very successful struggle against rats, humanity has used the most diverse means and, among other things, natural enemies of rats in the form of animals and microbes. Among the latter, special attention was paid to bacteria of the paratyphoid and Gartner groups. The following representatives of these groups were found in tame (white) and wild rats: Bact. paratyphyus B, Bact. paratyphyus A, Bact. enteritidis Gartner, and ratin bacteria similar to the latter, which include: Bact. Danysz, Bact. Issatchenko, Bact. Neumann, Bact. Trautmann, Bact. Dunbar, and the Liverpool bacterium. The attitude of rats to these bacteria varies. Paratyphoid bacteria A and B are weakly pathogenic for rats, causing a latent infection and carriage. Bacteria of the Gartner group, however, cause acute enteritis developing in the form of limited epizootics. Bact. enteritidis is especially pathogenic, but even it after some time leads to the development of immunity and carriage by rats. Ratin bacteria are the source of diseases proceeding in the form of septicemia and enteritis with the formation of characteristic bloody crusts around the eyes. Autopsy reveals an enlarged spleen, focal necroses, swollen lymph nodes and Peyer's patches, and blood-stained intestinal contents. According to Merezhkovsky, the Danysz bacterium kills 83% of rats (brown rats) in 5-8 days when fed. A certain percentage survive due to, as is assumed, immunity acquired by them. - The epidemiological significance of the listed bacteria normally present in rats lies in the fact that 1) as carriers, rats can spread these bacteria, e.g., in slaughterhouses to livestock meat; 2) when used to destroy rats, these bacteria can simultaneously lead to the poisoning of humans and domestic animals.

Bacteria of rat typhoid (one-day culture on agar).

In the USSR, Danysz cultures under the name "rat typhoid" (see figure) serve for the extermination of rats. Danysz isolated the microbe (from the Bact. enteritidis group) from an epizootic among field mice. He increased its virulence by passages in collodion sacs through the abdomen of rats. The Danysz bacterium, according to his personal experiments, as well as the experiments of Merezhkovsky and others, is harmless to humans and animals. However, a number of cases of poisoning by it in both animals and humans are known. According to Merezhkovsky, in cultures the Danysz bacterium loses its virulence, and to increase it, the general method of transitions (passages) through infected rats is used. During these passages, however, mixed infection easily occurs due to the frequent carriage by rats of paratyphoid and other bacteria of the Gartner group. Since the latter are indistinguishable even serologically from Danysz bacteria, rat typhoid cultures become dangerous due to the presence of Gartner bacteria. To maintain the virulence of Danysz bacteria in cultures, Merezhkovsky recommends a special nutrient medium consisting of hard-boiled chicken egg white, ground, mixed with water, and filtered. From these stock cultures, inoculations are made into meat-peptone broth to prepare the rat-exterminating liquid (see also Deratization).