Emergency Medicine Forum

I frequently travel on a medical mission trip to the Pantanal of Brazil to care for the indigent Indians living in remote villages.  I have always taken one of my children on the adventure (last trip I took 2 of my children).  Our team sleeps wherever we can, usually on the floor of a generous ranch owner who offers the space for us to sleep.  We put thin mats down, and then sleep on them.  These ranch homes are considered luxurious as they have running water (not hot, but when the temperature is 110F, who wants hot water?) and a working toilet (toilet paper not allowed—dispose of in garbage can).  They don’t have ovens, but instead cook over fire. The windows have wood closures (instead of glass), and on the evenings as it’s so hot, the windows are usually left open. (Last trip we left the door to my area open too, until the ranch owner warned of poisonous snakes that can come in during the night!) I always sleep in a bug proof tent on the floor somewhere (I put it on top of the mat). 

In contrast, Indians in the villages are lucky if they have a hose at the corner of the property that supplies water (otherwise they carry water on their heads from the river—frequently infested with piranha).  These village houses do not have toilets, but instead the Indians dig holes around their thatch homes for toilet purposes (convincing them to do this 10 feet or more from their houses has decreased the worm infestations some).  They also cook over fire (asthma is a problem as the ventilation in these one room thatch homes is not ideal).

On our last trip, my 15 y/o son was sleeping on the floor but declined a bug tent (to macho to worry about bugs).  One evening my son woke up and there was a dead bat on the mat (see the picture) about 10 inches from his feet (about 10 inches from the head of our pharmacist).  When the pharmacist woke up, he didn’t have his glasses on, and saw a black furry blob close to his head.   He initially thought it was a spider (they have black spiders that size….one was found about 10 feet from my tent the same morning…according to the ranch owner the spider ‘throws poison fur darts…very painful, but won’t kill you).  The pharmacist’s got up very slowly, and was pleased that it was only a dead bat and not a live spider. The bat must have flown in from the open window.  The dentist, the ophthalmologist, and an interpreter were also in the room sleeping on mats.  No one reports getting bitten.

Questions:

1. Should I worry about rabies?
 
In the US, wild animals accounted for 92% of reported cases.  Raccoons continue to be the most rabid wildlife species in the US (37.7% of all animals tested in 2006 were positive) followed by bats (24.4% tested were positive), then foxes (6.2% tested were positive). (1) Domestic species accounted for 8% of all rabid animals reported in the US in 2006.  Cats are more likely rabid compared to dogs.  In fact, the number of rabies cases reported in cats is 3-4 times that of rabies in cattle or dogs.  (1) 

There has been several case reports of rabies contracted without a history of a bite, but rather only a history of a bat in the room of sleeping individuals. Because those sleeping may not be aware of a minor bite or other mucus membrane exposure, the CDC recommends rabies post exposure prophylaxis unless the bat is available for testing.  (2)

2. How is the infection manifest in humans?

After exposure, the incubation period can last days to months (3) The average incubation period is 3 months.  (4) The first symptoms of rabies are very similar to a nonspecific viral infection with malaise, fever, and headache. (3)  Sometimes, if the bite site is identified, it may be painful or have paresthesia.  The acute period of the disease lasts about 2-10 days. After the acute infection, the patient will evolve into either the encephalitic (furious) or paralytic (dumb) form. Encephalitic rabies manifests as hyper-excitability, autonomic dysfunction, and hydrophobia.  Quadriparesis with sphincter involvement is characteristic of paralytic rabies.  (5)

3. How do you care for a possible bite from a rabid animal?

Local wound care includes debridement of devitalized tissue.  This will help reduce the viral inoculums. Do not suture any wounds suspected of harboring rabies as this may also increase the virus replication. (6)  Contact with the public health department will help in the assessment of risk of rabies to determine if rabies post exposure prophylaxis should be started. 

If you do decide to treat for possible rabies exposure, you will need to administer both the first of several rabies vaccinations, and also rabies immunoglobulin.  The immunoglobulin will neutralize the virus before its invasion of the CNS symptom.  It is believed that the antibody will not pass the blood brain barrier, and therefore is not likely helpful for any virus already in the CNS. (5)

4. What state is rabies free?

Interestingly, Hawaii is still rabies free, as of 2006 (1)

Outcome:

I suspected those exposed to the dead bat while sleeping needed rabies vaccine and immunoglobulin (there was no way to get the bat tested).  I remembered reading about rabies in an infant without a bite, but a dead bat found in the bedroom was considered the source, and that the CDC was now recommending vaccination in those situations.  I also knew that the average incubation time was 3 months.  I told them I thought they would need rabies vaccinations and immunoglobulin when they returned, and they didn’t believe me. (They thought I was joking.) I didn’t want to worry them, so I didn’t say anything more at that time.  We returned 5 days later, and I contacted both the public health department and our own infectious disease experts, and they both agreed that those exposed needed the vaccine and immunoglobulin.  My son refused to go initially (he thought I was overreacting), until I told him that all the others were also getting vaccinated.  Ultimately, they were all vaccinated uneventfully.  I guess its one of the perils of sleeping in the jungle.

In hindsight, I wonder if I should have aborted the trip and brought my son home for the shots.  We have evacuation health insurance when we go, so we can get to the US if we need to.  I guess I’ll never know if I was being to risky waiting till we got home to start the shots.

References:
1.  Rabies Epidemiology, United States Rabies Surveillance Data 2006.  Accessed at:  http://www.cdc.gov/rabies/epidemiology.html
2.  What to do if you have a potential rabies exposure. CDC Bats Sept 3, 2007 Accessed at:  http://www.cdc.gov/RABIES/exposure/types.html
3. Rabies Natural History of Rabies.  CDC. Accessed at:  http://www.cdc.gov/rabies/history.html
4.  Smith M Rabies Rescue Protocol Fails in New Cases.  Medpage Today.   April 20 Accessed at:  http://www.medpagetoday.com/InfectiousDisease/GeneralInfectiousDisease/5475
5.  Jackson AC< Warrell MJ, Rupprecht CE. Et al.  Management of Rabies in Humans  CID Jan 2003 35: 60-63.  Entire manuscript Accessed at: http://www.cdc.gov/rabies/docs/management.pdf
6.  Weber DJ, Hansen AR: Infections resulting from animal bites.  Infect Dis Clin North Am 5:663 1991.  Accessed at: http://www.ncbi.nlm.nih.gov/pubmed/1955705?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum