Can a Mosquito Kill a Killer Whale? Yes, Says New Case Report

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Little mosquitoes cause a big problem for orcas. Image by the US Department of Agriculture

How on Earth Do You Protect an Orca from Mosquitoes?

Mosquito control is always a challenge particularly in areas prone to high activity. But for orcas, it’s virtually impossible, suggests Jett.  “There has been surprisingly little research done on protecting zoo animals from biting mosquitoes,” he explained, “we cite Derraik (2005) who advocates primarily managing standing water (i.e., eliminating breeding habitat) and enclosing animals in wire mesh, although this is obviously not possible with whales.”

Also included in the paper is a satellite photo showing water bodies adjacent to Shamu Stadium in Florida. Shamu Stadium is the primary performance arena for SeaWorld’s orcas. “I can’t imagine an effective strategy to mitigate this potential problem,” Jett said, “further, topical repellents are simply not feasible as most of these are easily washed off, and many are potentially toxic.”

There is also the size of an orca to contend with. Tilikum for example, SeaWorld’s prime breeding bull, measures 22.5 feet (6.9 m) long and weighs 12,000 pounds (5,400 kg). “Covering their entire dorsal surfaces with repellents is problematic,” Jett said, adding that “there are currently no effective vaccinations to protect against these viruses.”

Increasing Concerns over US Army-Developed DEET

Concerns over the use of the registered pesticide called DEET (chemical name, N,N-diethyl-meta-toluamide) are mounting, particularly its potential effects on the central nervous system. As such, it would prove problematic for orcas.

Jett explained that although the pesticide is “the only truly effective topical repellent, there is an entire body of literature on the harmful effects of DEET.” And as for fogging, this is also out. “We cite literature that mosquito fogging such as the kind that some municipalities adopt in the summer is mostly ineffective,” Jett said.

In short, when it comes to marine parks located within WNV and SLEV-prone geographic locations Jett concluded, captive marine parks are “left without any tenable strategies,” to prevent disease transmission. Dr. Jeffrey Ventre is a medical doctor who specializes in Physical Medicine and Rehabilitation (PM&R). He added:

Although the narrow focus of our paper was the death of two particular captive killer whales, by mosquito, it has broader implications. In looking at the factors that caused immunosuppression in the first place (and made Taku and Kanduke susceptible) we were able to review several of the negative consequences associated with captivity itself. This is, as far as we know, the first time these protected trade secrets, such as teeth drilling (via pulpotomy), deconditioning, and high UV dosing, have been openly discussed in the peer reviewed literature. We certainly hope it will lead to more science.

 Orcas and Mosquitos: Time to Pay Attention

Although there is not currently a safe preventative measure to protect orcas, or other large captive marine mammals, from mosquitoes, identifying the cause of the problem is a good first step. As Dr. Ventre suggests, discussing these issues openly in peer-reviewed literature may lead to more research, potentially saving lives down the line.

 

Sources:

Jett, John. Ventre, Jeffrey. Orca (Orcinus Orca) Captivity and Vulnerability to Mosquito-transmitted Viruses. (2013). Journal of Marine Animals and Their Ecology. Vol. 5, No.2. Accessed May 14, 2013.

U.S. CDC. West Nile Virus, Pregnancy and Breastfeeding. (2012). Accessed May 14, 2013.

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