4th Rabid Bat Detected in Fremont

Rabid bats in Alameda County!

We are up to 12 rabid bats detected in Alameda County during 2015. Four from Fremont, three from Sunol, two each from Pleasanton and Livermore, and one from San Leandro.

There have been four different species of bats detected; 8 Tardarida brasilliensis (Mexican Free-tailed bat), 2 Myotis (Little brown bat), 1 Lasiurus cinereus (Hoary Bat), and1 Corynorhinus townsendii (Townsend’s big-eared bat). Interestingly, all four bats from Fremont were Mexican Free-tailed bats and Livermore had the interesting Hoary bat and Townsend’s big-eared bat.

Information on Northern California bats can be found here: http://www.norcalbats.org/aboutbats.shtml

We may never know for sure what environmental pressure has instigated these bats to develop rabies, but we might suspect the striking situation of the drought, and unseasonably warm weather last winter may have contributed. Some individual bats in the bat population have the rabies virus, but the virus is usually subdued by their immune system, though this situation not well understood.

Here is a link to an interesting video at IFL Science that tries to shed some light: http://www.iflscience.com/plants-and-animals/why-do-bats-transmit-so-many-diseases

What we have to keep in mind is that this is a “passive” surveillance system, and only the bats that are reported, and are in testable condition, are tested. There may be many other bats that have have died of rabies in bushes and other obscure areas.

The Alameda County Public Health Laboratory has tested about 55 bats so far this year, 29 of which were Myotis bats, 18 Mexican Free-tailed bats, 4, Hoary bats, 2 Pallid bats, and one Townsend’s big-eared bat. From this testing we see about 45% (8/18) of the Mexican Free-tailed bats were positive for rabies, and only 7% (2/29) of the Myotis bats were positive for rabies. The Hoary bats had a 25% positive rabies (1/4), and the Townsend’s Big-Eared bat had 100% (1/1), though these are small sample sizes. Overall, we have a 22% positive for rabies rate from the 55 bats tested so far this year (as of last Friday).

A note from the Statewide animal rabies perspective: 117 bats, 12 skunks, 2 cats and 1 coyote were detected with rabies, as of September 9th, 2015. At the publishing of these statewide statistics, they have only had 11 rabid bats reported from Alameda County, but the Alameda County positives make up 9.4% of all detected rabid bats. This is understandable when you know that Alameda County is ranked 49th by land area, but 7th in population in the state of California. This tells me we have more eyes on the ground, and a population that is very participatory in our rabies surveillance program!

We have a rich population of bats in Alameda County, and are fortunate to have these interesting insectivores, but caution should always be taken when encountering wild animals. If you encounter a bat in an unusual situation, call Alameda County Vector Control (510-567-6800), or your local animal control, and have the professional assess the risk of the situation. A bat flopping on the ground is a sure sign of a problem, but a bat resting on a bush during the day, may be a normal situation for a “solitary” type of bat. The Mexican Free-tailed bats are a “colonial” type of bat, and normally return to the colony residing in a secluded area by daybreak. Always keep your pets rabies vaccination up-to-date, because an unvaccinated pet may encounter and have contact with a rabid animal without your knowledge, and put your whole family at risk! Also, unvaccinated, or lapsed vaccinated pets usually will have to undergo a 6-month rabies quarantine.

Daniel Wilson, Community Relations

Alameda County Vector Control

daniel.wilson@acgov.org