An insidious invader, the rabies virus threatens Southern Ontario. The province’s Ministry of Natural Resources and Forestry (MNRF), which operates a fleet of De Havilland Canada Twin Otters and Turbo Beavers, Canadair CL-415 waterbombers, and Airbus AS350 B2 and EC130 B4 helicopters, wages a yearly battle to slow the spread of the deadly neurological disease.

When rabies infects its host, like a parasite, it causes aggressive behavior in an attempt to self-preserve and replicate. Each year, roughly 60,000 people are killed worldwide by the disease, driven mainly by dog bites in developing regions. Once the disease is transmitted and established, the death rate is over 99 percent in humans. Thanks to the MNRF’s annual rabies bait drop program, wild animals like racoons, foxes, and skunks are vaccinated while chewing on sweet-smelling bait distributed both by aircraft and by hand on the ground.

Every year from June to mid-September, over 715,000 baits are distributed across Southern and parts of Eastern Ontario. The 4.3-gram baits are made of non-hazardous, food-grade components, and contain a capsule of the vaccine that is easily ruptured by chewing to inoculate the animal orally.

The MNRF’s campaign in Southern Ontario covers an area of 10,000 square kilometers (3,860 square miles), from the Niagara region westward to the Regional Municipality of Waterloo; areas of Eastern Ontario, like Frontenac County, are also targeted.

Roughly 78 percent of the distribution is done by aerial drops from a slightly modified, bright yellow De Havilland Twin Otter operated by the MNRF’s aviation branch. In smaller target areas where it is impractical to fly the Twin Otter — like stretches of green space along the Niagara River — a MNRF EC130 B4 helicopter is employed, providing a wall of defense from wildlife making their way across the Niagara River from New York State. Any remaining pockets are baited by hand on the ground.

Systems and Patterns

The Twin Otter flies a special distribution pattern on a north-south axis, approximately 750 meters (2,460 feet) apart. The target distribution density is predetermined before the flight and factors in terrain, tree cover, urban areas, and agricultural use. Typical target density is 75 baits per square kilometer, while some hot spots and established migration routes receive as much as 150 baits per square kilometer.

To make the distribution process more efficient, the Twin Otter is equipped with a conveyor belt system, which is controlled by a computer — connected to the aircraft’s GPS — that has a series of flight profiles programmed into it. The conveyor system is known as the “Vaccine Bait Dropping Machine,” and is a specialty unit that is continuously evolving.  

The original bait machine was designed and manufactured by Demand Maintenance & Machining in Pickering, Ontario, and included an electronic control panel created by Redford Robotics in 1989. There have been several modifications since. The current system, which includes the conveyor, was developed by OES Inc. of London, Ontario, in conjunction with Queen’s University. Each year, the system is installed temporarily in one of the MNRF’s six Twin Otters.

The ministry holds the supplemental type certificate for specialty conveyor equipment configured specifically for the Twin Otter. The only external modification required on the aircraft is a drop chute panel that is installed in the rear belly of the fuselage.

In order to maintain the bait dispensing rate required to achieve the target density, the speed of the conveyor is adjusted based on the aircraft’s speed. GPS tracks, as well as the number of baits dispensed, are logged by the computer and are used for mapping to review where baits were dropped.

On board the specially equipped Twin Otter is a crew consisting of a pilot, a flight engineer, and two technicians in the back of the plane who load the conveyor. The flight engineer operates the conveyor from the co-pilot seat and drops the baits in the appropriate locations.

On the EC130 B4, the bait-dropping system is much less complex as distribution is simply done by hand; baits in predetermined quantities are tossed out the open side door of the helicopter, and the actual drop locations are determined by visual reference.

Once the targeted animals take the bait, it takes 14 days for the vaccine to become fully effective, and the animal attains high immunity to infection for one year.

Preparing for Takeoff

The Brantford Municipal Airport (CYFD) serves as the Twin Otter’s base of operations, with flights heading both east and west from this central location. The airport’s British Commonwealth Air Training Plan triangular runway configuration, combined with the Twin Otter’s short takeoff and landing ability, make for an any-wind-direction operation. However, flights can still be impacted by non-visual flight rules (VFR) conditions, and the potentially stormy summer weather in Southern Ontario.

The baiting distribution in Eastern Ontario begins with the Twin Otter in early August, while distribution in Southern Ontario takes place mid-to-late August utilizing both the Twin Otter and EC130 B4. The late summer timing of the campaign is based both on when wildlife is most active and when juveniles are present and old enough to consume the baits.

Prior to each bait distribution flight in the Twin Otter, the tracks and flight profiles are built using geographic information system company Esri’s ArcGIS software, which defines the baiting area, the track spacing, and density parameters. The distribution zones are first mapped out and transferred to Google Earth, where the individual flight tracks are laid out. These coordinates are then loaded into a Garmin GPS in the aircraft.

Over the course of a week, four sorties are typically flown each day, with each sortie lasting from one hour to 2.5 hours, depending on transit times. This translates to 20-30 sorties and 60-80 total hours flown in an aerial baiting season.

Every flight is flown by hand with dead reckoning and no autopilot, at a speed of around 150 knots and an altitude of 300 feet above ground level. This puts the Twin Otter and crew in a vulnerable position for extended periods of time, with hazards like birds, wind turbine generators, communication towers, and other aircraft operating out of small fields.

The MNRF said the Twin Otter is the ideal platform for this type of mission, thanks to its second engine, its wide flight envelope, and large cargo capacity.

Using Data

The MNRF began researching rabies control methods in the 1980s. Previous approaches relied on mass extermination attempts of carrier species through trapping and hunting. Like many before them, these plans failed due to their unsustainable nature — causing the targeted species to rebound even more once human intervention subsided. It is far easier to intervene through an animal’s natural hunger drive than trying to eradicate it altogether.

When raccoon strain rabies first invaded Ontario in 1999, a large-scale elimination program was initiated and managed to eliminate the outbreak by 2005. However, in 2015, raccoon strain rabies entered Ontario once again, causing another outbreak. Since then, the province’s rabies control program has been effective in containing the most recent outbreak within 65 km of the initial case, and overall cases have declined in Ontario by 95 percent since 2016. As of late 2022, terrestrial rabies cases have been restricted to the small geographic area of St. Catharines, Ontario. (The last case of fox strain rabies diagnosed in Ontario was in 2018.)

The efficacy of the MNRF’s program is measured through an adaptive management approach — continually reviewing methods and considering new ideas. Evaluations of different bait densities and distribution methods, how quickly baits are consumed by wildlife, and what species consume the baits — as well as collecting blood samples from live-trapped raccoons and skunks — help estimate what proportion of the raccoon and skunk populations were vaccinated during the annual baiting campaign. In addition to monitoring the number and location of rabies cases, collaboration on several rabies research projects enhances the understanding of the virus and ways to improve the control program. 

“These studies help to maximize effectiveness and progress toward the goal of eliminating terrestrial rabies in Ontario,” the MNRF said.

Essential Work

In 2021, 14 cases of raccoon strain rabies were detected in Ontario — all in the Niagara region. This is up from the nine cases detected in 2020, but a far cry from the 255 cases detected in 2016 — following the 2015 rabies outbreak.

Thanks to prevention and control programs such as the one implemented by the MNRF, human rabies cases are rare in Canada. In fact, Ontario’s last domestic case of human rabies occurred in 1967. Without proper control, rabies would spread approximately 50 km (31 miles) per year, the ministry said.

Since 2015, the MNRF has distributed over 7.5 million vaccine baits and has tested more than 25,000 wildlife samples. During last year’s rabies baiting season, a team of 35 staff — including field and lab technicians, biologists, and a communications specialist — dedicated hundreds of hours to the program.

Of course, pilots played a critical role, too. There are currently 47 fixed-wing and 19 rotary-wing pilots working for the MNRF’s aviation branch, which supports a variety of missions in addition to aerial rabies baiting, including forest fire suppression and numerous other specialty provincial resource management programs. However, the ministry noted that, just like the rest of the aviation industry, it experiences challenges with staff levels from time to time. 

“The aviation talent pool is constantly shifting, and the ability to hire the best and brightest human resources can sometimes be challenging and typically ebbs and flows,” said the MNRF. 

The ministry noted that, at the time being, its current team of pilots is sufficient for its operations.

As the 2023 summer season approaches, the MNRF is gearing up for yet another year of its vaccine bait drop program — known as one of the most successful rabies control plans in all of North America.