Thursday, August 24, 2017

Murine typhus on rise in Texas

Researchers from the Baylor College of Medicine and Texas Department of State Health Services recently reported an increase in the number of reported cases of typhus in Texas. Texas historically has had more cases of typhus than other states, but this new study published in the CDC's Emerging Infectious Disease journal  shows that numbers of cases have increased ten-fold in the past 14 years.

When rodents are present in a house, there may also be rat fleas.
The oriental rat flea is thought to be the principal vector of
murine typhus, a disease on the rise in Texas. (Image courtesy
Pest and Diseases Image Library,
In addition to a general increase in cases statewide, the data shows that what used to be solely a south Texas problem is creeping into more northerly parts of the state. Houston, for example, which had no cases of typhus as recently as 2007, reported 32 cases last year.  Nueces County, home to the city of Corpus Christi, had the highest case rate in Texas, reporting about 140 cases/100,000 population.

The causative agent for murine typhus (the term "murine" is a scientific term referring to rodents) is a rickettsial parasite called Rickettsia typhi. This parasite is always present in rodent populations, both Norway and roof rats, and to a lesser extent mice and opossums.  The primary vector that transmits the parasite from rodent to rodent, and occasionally to humans, is the oriental rat flea, Xenopsylla cheopis, though other fleas, including the cat flea are suspected to be occasional vectors.

Symptoms of murine typhus include fever, headache and rash. Left untreated, the disease can be fatal in about 2% of cases; but once diagnosed, typhus is easily treated. Numbers of cases peak during the summer months of June and July, but in south Texas there is a secondary peak in cases during the winter.

The typhus pathogen is thought to infect people when they scratch an itchy flea bite. It is present in the flea's feces, which may be rubbed into the site of the bite during scratching.

While the exact cause for the increase in typhus cases is unknown, pest control will play an important role in any solution. Experience with murine typhus in the past has shown that cases peak when flea numbers are highest, and that case frequency declines when rats are controlled, and insecticides applied for fleas.

In 54% of the cases reported in this study, fleas were reported to be present in the home, and 34% of patients recalled a flea bite.  Rodents were known to be present by the victims in about 29% of the cases, and some form of other wildlife was present in 42% of cases.

Good flea control, rodent exclusion and rodent control are among the most important public health services our industry provides. So if you didn't have enough reasons to explain to customers why they need you, you now have one more.

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