Do rats have a dry bite?


What is a dry bite?

Among rat enthusiasts, a "dry bite" is a bite without saliva.

Rat are believed to have a dry bite because their incisors are so far foward in the mouth that they don't get coated with saliva. Therefore, rats are believed to be incapable of transmitting saliva-borne diseases.

The dry bite hypothesis is usually mentioned in the context of rabies transmission: rats are believed to be incapable of transmitting rabies (a saliva-borne disease) because of their dry bite.

Do rats have a dry bite?

No. The rat dry bite idea is a myth. Rats have a wet bite and can transmit saliva-borne diseases. Here's the evidence:

Rats transmit saliva when they bite

Wong et al. (1984) report a case of a patient who developed a swelling around the site of a rat bite. Later allergy testing on the patient's skin showed that the patient had a rare allergy to rat saliva and to chemicals found in the saliva of the rat that bit him. These allergy tests show that the rat's bite transmitted saliva to the patient.

Rats can transmit saliva-borne diseases

Saliva-borne diseases transmitted by rat bite include rat bite fever (Downing et al. 2001, Graves and Janda 2001, Grude 2001, Schuurman et al. 1998, Hagelskjaer et al. 1998, Hockman et al. 2000, Weber 1982), ratpox/cowpox (Marennnikova et al 1988, Postma et al. 1991), and extremely rarely, rabies.

Rabies from rats is very rare and has never been documented in the United States. However, a handful of cases of rabies from a rat bite have been recorded in Poland (Zmudziñski and Smreczak 1995, described in Wincewicz 2002), Israel (Gdalevich et al. 2000), Thailand (Kamoltham et al. 2002) and Surinam (Verlinde et al 1975).

Contracting one of these diseases from a rat bite is a rare occurence, but the fact that it can occur shows that rats can transmit saliva-borne diseases.

Other animals with forward-placed incisors transmit saliva-borne diseases

If foward-placed incisors make a bite dry, then other species with forward-placed incisors (e.g. other rodent species, rabbits) should have a dry bite too and should also be incapable of transmitting saliva-borne diseases or causing humans to have an allergic reaction to their saliva.

However, other rodent and rabbit species have been shown to transmit diseases in their saliva. For example, woodchucks and rabbits (e.g. Childs et al. 1997, Moro et al. 1991), squirrels (e.g. Magee et al. 1989, Olson et al. 1988) and prairie dogs (Alcala-Minagorre et al. 2004) transmit saliva-borne diseases. Hamster and prairie dog bites have, on occasion, caused anaphylaxis after a bite due to an allergen in their saliva (Lim et al. 2004, Onaka et al. 2004).


Rats do not have a dry bite: they can transmit saliva when they bite. Rats therefore can, and do, transmit saliva-borne diseases. These diseases are rare, but the fact they are transmitted refutes the dry-bite hypothesis.

As the dry bite hypothesis usually comes up in the context of rabies tramsmission, note that rats almost never carry rabies and are not considered a serious rabies risk. Rabies transmission from rats is extremely rare, not because rats have a dry bite, but because they almost never carry rabies, presumably because rats do not survive the attack of a rabid animal.

Lastly, the term dry bite is a real term. It refers, not to a "salivaless" bite, but to a bite without venom from a venomous animal such as a rattlesnake or a spider.