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.

Understanding chikungunya

The black and white Asian tiger mosquito is one of the two most common potential vectors of chikungunya nationwide

Fortunately for all of us who live and work in the U.S., insect-borne disease is not rampant in our country. But this isn't something to take for granted either, as we have seen this summer with the rapid spread of the chikungunya (chik-un-GOON-ya) virus throughout the Caribbean.

Over 30 years ago as a graduate student taking a course in medical entomology, I learned about all kinds of diseases spread by insects.  By far, most of these were tropical and exotic-sounding. Chikungunya virus was one of those diseases I memorized way back then, and have since mostly forgotten.

Chikungunya was first described in 1952 during an outbreak in southern Tanzania (east Africa).  The name comes from the Makonde language and means "that which bends up", referring to the contorted, bent-over appearance due to joint pain suffered by those who contract the disease.  Sounds bad, doesn't it?

While not as serious as some mosquito-borne diseases, including malaria or Eastern equine encephalitis, or even the neurological form of West Nile virus, this virus is nothing to sneeze at.  While some people have mild cases, it frequently comes with a very bad headache, joint pain, rash and fever.  There is no treatment for chikungunya, and there is no vaccine to protect you if you go where the disease is active.

When I learned about chikungunya in college, it was found only in eastern Africa and parts of India and Southeast Asia.  That distribution has spread in recent years as outbreaks occurred in parts of western Africa and Europe.  In December 2013 the first epidemic on our side of the world was reported when the disease made the jump into the islands of the Caribbean.  Since the beginning of 2014 the disease has been spreading like wildfire, with more than a quarter million cases, and over 20 fatalities in the Caribbean. 

Chikungunya has been on the radar of U.S. health officials in recent years largely because its vectors are very common in our country.  The principal mosquito vectors of chikungunya are in the genus Aedes. They include the Asian tiger mosquito, Aedes albopictus, and its close relative, the yellow fever mosquito, Aedes aegypti. These are the species that inevitably bite me whenever I chance a trip outside without repellent in my backyard here in the Dallas area.

Unlike West Nile virus, birds are not a part of the chikungunya disease cycle.  As far as we know, the virus is only viable in mosquitoes and primates.  In Africa, the disease lurks both within humans and non-human primates, such as baboons and monkeys.  For the virus to take hold here in the U.S., it would have to be common enough to reach an epidemic tipping point.  This would occur when enough people were infected to start a cycle from human to mosquito to human again.

We may not have yet reached that tipping point, but we could get there easily.  In July the first locally acquired cases were reported in Florida. These were the first cases where the victims had not recently traveled to the Caribbean, or other places where the disease is endemic. According to the CDC, between 2006 and 2013 the U.S. averaged about 28 cases of chikungunya annually from travelers. In the first six months of 2014 alone there were 243 travel-associated cases in the U.S.  And, according to a July 15 release by the Texas Department of State Health Services, five cases have been reported in Texas so far this summer.

So should you or your customers be worried about chikungunya?  If you plan travel to the Caribbean this year, definitely!  Make sure to carry repellent and use it liberally during your travels to any Caribbean island. At home there is little risk yet; but this could change.  As the number of sick travelers returning from Caribbean cruises and high school missions trips increases, the risk of locally acquired chikungunya will increase.

All of this increases the value and importance of all residential pest control services, especially where Aedes mosquitoes are active. Technicians servicing homes should be on the lookout for any sources of standing water.  These may take the form of storm sewer catchment basins, leaking septic systems, containers or plastic items that catch and hold water, house plant pots with dishes that hold water, bird baths, wheel barrows, boat covers and other items. You may not be servicing your account specifically for mosquitoes, but pointing out mosquito risk factors is an add-on service to your customer and can increase your value in their eyes.

If you have a newsletter or email service to your customers, now's a great time to remind them of the four Ds:

• Drain and dump standing water 
• Dusk and dawn are the highest risk times for mosquitoes (though the Aedes mosquitoes are active all day) 
• Dress in long sleeved shirts and long pants when outdoors 
• DEET is an ingredient to look for in your insect repellent (or another effective choice such as lemon oil of eucalyptus, picaridin, p-menthane 3,8-diol or IR3535). 

For more information about where mosquitoes can breed, and how to identify Aedes and other mosquitoes, see http://mosquitosafari.tamu.edu