Rats in the news

Norway rats scavenge left-over people food
in a New York city park. Photo by Mailman
School of Public Health, Columbia University.

Perhaps appropriate for the Halloween season, rats and rat mites have been in the news recently. It was reported last week that a study conducted on New York City rats found that rats carry even more diseases than we previously thought.  Scientists at the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health identified several bacterial pathogens, including an E. coli, Salmonella, and Clostridium difficile, that cause mild to life-threatening gastroenteritis in people; Bartonella bacteria; and Seoul hantavirus, which causes Ebola-like hemorrhagic fever and kidney failure in humans. The study highlights the prevalence of these diseases in wild urban rodent populations, and the real risk of acute stomach and febrile illnesses carried to people from rodents.

The authors state that the study shows a need for improved pathogen surveillance and disease monitoring in urban environments.  I would add that these results also show the importance of rodent control to human health, as well as the need for pest management professionals to take precautions when handling dead rodents.

Along with the NYC rat report, came coverage last week of rat mites.  One reporter called them a worse scourge than bed bugs... something I disagree with, but a story that is sure to resonate with some of your customers with suspected mite problems.

Rat mites are tiny parasites that principally attack rodents.  The primary homes of rat mites are in the nests of rats and mice; but when the rodents are trapped or exterminated, the resident mite population may abandon the nest in search of other hosts.  Though rat mites cannot live on human blood, they will bite people, often leaving a red mark and blister.

The reason I don't consider rat mites to be as troublesome a pest as bed bugs is that rodent control will ultimately eliminate a rat mite problem--though mite control in a structure may still be needed to clean up residual mites that can linger in a home for several months.

The other, more scholarly story in the news this week is a study that appears to show a connection between rat mites and Bartonella infections in two dogs and a human.  In a study reported by researchers from North Carolina State University, several raccoons were trapped and removed from a New York home.  After removal, the house living area became infested with rat mites, Ornithonyssus bacoti, many of which were removed from the animals and some of which were collected by the homeowner.  Both the dogs and the homeowner subsequently became ill, and blood tests revealed the presence of Bartonella henselea, a bacterial pathogen best known for causing "cat scratch disease".

Bartonella is known to be transmitted from cats and dogs via fleas and ticks, but this was the first time rat mites have been implicated in transmission (It's important to note that the researchers couldn't conclusively prove that the mites transmitted the disease, as ticks were also found on one dog. Also they did not rule out the presence of rodents or fleas in the home, but the timing and series of the events, along with the large number of mites and visible bites on both dogs and the person in the house provide good circumstantial evidence of the mite's role).

I gleaned a couple of points from this paper.  First, although the paper did not in my mind conclusively prove the raccoon as host and source of the mites, the close association of the raccoon removal and mite infestation seem to suggest that rat mites could infest raccoons. Raccoons are a relatively common wildlife invader of homes in Texas and throughout the U.S., and these results potentially impact many pest control jobs.  Second, I was unaware of the potential disease problem associated with rat mites.  The potential for rat mites to transmit disease appears to be low, or else there would be many more instances in the literature; nevertheless, this paper is something we in the pest control industry should be aware of--not only for our customers, but also when treating for rodent or bird mites. If a technician is going into a situation with lots of biting mites, it would be prudent to provide protective gear, including gloves and protective overalls sealed at ankles and wrists.

Lastly, I was reminded that when a real rodent mite problem exists, it is normally not too difficult to collect mites.  In this case the homeowner had no problem seeing and collecting mites for the pest control company and researchers.  This is not the case with many submitters of "mites" to my office. This year I've received dozens of samples of suspected mites from people who are convinced they are being attacked by mites. In most of these cases the sample submitters have been unable to provide an actual mite specimen. This is often a case of a misinformed customer who has been led astray by poor information on the Internet, or from poorly informed friends. For customers who will not take a diagnosis of no mites, regardless of repeated efforts to get samples, the situation may be one of delusions.

Once again the importance of pest control is supported by scientific research. It's important for you and your employees to remember every day that the service your pest control company provides is important. Rodents simply cannot be tolerated in homes, schools, food plants, businesses or multifamily apartments.  And it's not just a matter of aesthetics. Even when rodents are present but out of sight, remember that many rodent diseases are transmitted by airborne dust from rodent urine and droppings.  It's critical that we are protected not just from seeing rodents, but from being exposed in any form to rodents in our buildings.

If we're talking scary, forget the zombie costumes or Ebola scare stories this Halloween.  A much more real risk is that of unwanted contact with rodents and their mites and diseases.