West Nile Virus
Maximizing Prevention

by David T. Longo

Longo’s Aviaries Inc.
Meaford, Ontario, Canada

What is West Nile Virus and why is it a cause for concern? It is a virus that is spread only by the bites of infected arthropods. It may cause encephalitis (inflammation of the brain) and also may cause myocarditis (inflammation of heart muscles). Of the arthropods, mosquitoes are the main carriers (at least 43 species worldwide) and, to a lesser extent, ticks. There is no evidence of direct animal to animal, or animal to human transmission.
Wild birds are the primary hosts for WNV but the virus may also infect humans, domestic fowl, large domestic animals, and non-human primates. Prior to 1999, the virus was only reported from Africa, Asia and Europe, and had never been found in the Western Hemisphere. Incubation period is 5-15 days following bite of infected mosquito.

The 1999 New York outbreak of West Nile Virus caused disease in at least 60 humans and resulted in 7 deaths among them. It likely killed at least 5000 wild birds, mainly American Crows, but also caused deaths in at least 20 other species of native wild birds (American Robin, Bald Eagle, Black-billed Magpie, Black-crowned Night Heron, Blue Jay, Blyth’s Tragopan, Broad-winged Hawk, Bronze-winged Duck, Chilean Flamingo, Cooper’s Hawk, Cormorant, Impeyan Pheasant, Laughing Gull, Mallard, Sandhill Crane, Snowy Owl, Red-tailed Hawk, Ring-billed Gull, Rock Dove, and Yellow-billed Cuckoo. Several species of Psittaciformes; the Ringed-neck Parakeet and the Vasa Parrot, and Cockatiel have also been shown to be susceptible to the WNV.

The virus also caused disease in at least 22 horses (at least 10 of which died or had to be euthanized) while at least 21 other horses became infected without showing any sign of disease. The following year, WNV migrated north and arrived in Windsor then in 2001 it migrated into the GTA. Since then it has been here in Canada and is migrating from region to region. In 2002 the incidence of it died in Ontario but took a long leap and hit in Saskatchewan, Alberta and Manitoba. Now in May of 2004, it is has already been found in Owen Sound, ON; less than 10km from our new operation.

Dr. Branson Ritchie at the University of Georgia is working with a research consortium on an avian-specific vaccine to prevent West Nile virus-associated disease. Reaching the level of treatment is the choice we do not want to have. To date, there have been several zoos in North America whom have been and still are vaccinating animals other than equines with vaccines that are primarily for equines. This is a temporary solution and should be used as a last resort to protect the animals until a vaccine will be specifically made for the other orders of animals. This was administered to several orders of birds and they accepted the vaccines poorly. In turn, this directly affects their ability to reproduce and offers them a permanent inferior quality of life.

Another not so effective method that is continually used is spraying with insecticides. Insecticides do indeed kill insects but is harmful to birds, aquatic organisms and bees of course. This procedure takes much longer to break down or has a slower solubility in the environment, generally the water and earth.

There are several other applications that work on the prevention level so as to not worry about reaching the stage of treatment. Stopping this problem in its tracks is essential!

When enclosing specimens susceptible to WNV in exhibits, mosquito netting is an ideal solution. We should first have a good framing plan for enforcing the netting. Reinforcement should be installed or mesh removed for winter months from snow payloads or its weight thereof. This can be one of the more expensive routes.

Stagnant water vs. Ponds; here is a situation where any body of water that has a lack of circulation, mosquitoes will lay their eggs. Dead circulation or stagnant water can exist in buckets, pots, car tires and tire depressions in small grain gravel and grass. All these elements should be removed and depressions in the ground (gravel, sand or grass) should be filled or flattened. Ponds should have complete circulation throughout all areas.

A sure fire prevention method is to introduce a small species of fish that consumes primarily mosquito larvae into these bodies of water. There are two that are used commonly, one, the Georgia Giant Bream that is being produced by the billions in the U.S.; scientific name of this species is Gambrusia holbrooki. There are fish farms that exist which specialize exclusively on this species. They can be acquired for as little as .4cents ea/US. Another option is the Golden Minnow which is not as aggressive. These are being used by a few aviculturists and colleagues of mine with great success.

If we refer to the food chain we just reviewed 1 of their predators. Another predator of the adult mosquito is Bats. We can introduce colonies of bats to desired regions by directly applying or installing bat houses. Some houses can hold colonies from 25 up to 100 or even 300 bats to each house. To put this idea into more perspective, one bat alone can consume more than 1,200 mosquitoes each hour. Location is crucially important to ensure their move into your habitat. The face of the bat house should be positioned towards the west so there is a minimum of 6-10 hours of exposed sunlight prior to sunset. This buildup of heat will ensure the house stays warm throughout the night. If it is too warm, it should be ventilated. Depending on where in North America and the climate will depend on the colour of the bat house and whether or not it requires ventilation. Bats generally follow bodies of water; streams, rivers and creeks where insects frequent. The house should be located approximately 400m or ¼ of a mile on either side of the water. We found evidence of bats at our new facility and built a large holding for the bats. It has only been installed in June of this season so occupancy may begin this year.

One of the better alternative methods is the Propane Mosquito Traps. This device converts propane into carbon dioxide that lures mosquitoes to the trap. There is also heat and a blue light that also draws them closer until the trap vacuums them into the capture chamber. It only serves ¾ of an acre and does have to be plugged in. It does not let off any toxic fumes, so relocation can be suited if you have a long enough extension cord. At $300.00 each unit they are not that expensive but when dealing with larger zoological institutions, acreages becomes a factor or these can be applied only to the subjects’ areas that are susceptible to WNV.

If we are to completely minimize WNV, we have to stop the carrier. Utilizing all these methods mentioned and more will optimize the absence of WNV. Chances are less than 0.001% any animals will contract WNV if all these applications are introduced. Eliminating mosquitoes from the premise is one of the key elements to fulfilling our responsibilities in maintaining these animals in their peak performance, health and behaviour. Only when they are in these conditions, are they most advantageous when both exposing them to and educating the public.

Dave T. Longo
Longo's Aviaries Inc.
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