Remote Drug Delivery System (RDDS) for Wild Life Administration
In 1950s, while working on introduced wild goat, deer and tahr population in New Zealand, Christchurch born pharmacist, veterinarian and inventor Sir Collin A. Murdoch came up with an idea of developing a remote or ballistic drug delivery system to tranquilise animals. Having experience with repairing and modifying rifles in World War II, Murdoch invented various rifles, darts and pistols which have been an important part of animal studies/treatment/control around the globe. He established the Paxarms Limited which still sells various ballistic tranquilising systems. Generally, a RDDS contains a projector and a dart with four components, including a storage space for drug(s), an injective part for loading drug, a needle to penetrate the skin and a stabiliser for ballistic accuracy (West, Heard, & Caulkett, 2014). Such systems can deliver the medicines to wild animals at a safe distance, avoiding the risks of anesthetisation and direct contact with animals.
Remote drug delivery has become an essential tool for safely delivering medication and vaccines to free-ranging, non-domestic, or dangerous animals. All dart guns currently use a single dart per injection, and it might occasionally be not practical with large animals. Shooting the dart more than once on an animal may cause flight, injury, stress, and ultimately unsuccessful delivery. Furthermore, purchasing many dart guns and hiring and training more staff may be unfeasible in developing countries. Therefore, employing the double-dart injection technique may help reduce the cost of operation, save time for capturing animals, minimize stress and injury, and improve animal welfare.
Remote drug delivery has become an important tool for allowing the capture and safe delivery of medication and vaccines to free-ranging animals, zoo animals, marine animals, and wildlife. This method ensures safety for veterinarians, zookeepers, game captures, and wildlife researchers. . The two main types of remote injection equipment commonly used in zoos are blowpipes and dart guns. Blowpipes have been used by local people for more than a century to capture animals and fight . It has been applied to use with an auto-syrinx dart to deliver the drug to many animals with a shorter shooting range than the dart gun . Dart gun injection is a widely accepted and routine procedure for administering anesthesia to various animals, including dangerous animals . In large animals such as elephants, the dart gun injection is vital to manage the violence caused by musth elephant and wild elephant-human conflicts. Wild elephant-human conflicts are found in many countries, including Thailand, leading to human and elephant injury and death, as well as property damage . Injections of tranquilizers and anesthesia have been used to calm down and move these animals . When working with large or mega animals, the volume of the drug usually increases accordingly with the size of the animal. There are circumstances in which there is a lack of availability of large-volume darts for various reasons in the field. The immediate solution is to put the drug into two darts and shoot twice. However, the first shot can lead the animal to become frightened and escape, creating stress and leading to injury or death in the worst-case scenario.
The problem may be fixed by having two guns and two professional staff, but this strategy would cost more money to buy guns, hire more staff, and do training. Hence, this solution is usually impractical in developing countries . The double-dart injection technique might be an additional or alternative technique helping field officers reduce loss and injury in specific conditions that may happen. Occasionally, a lack of large-volume darts may arise, creating a life-or-death emergency for animals and humans. Furthermore, this technique could assist with treating sick animals that require two kinds of drugs simultaneously. Therefore, knowing the double-dart injection technique with proper guidelines can help manage this situation. We hypothesized that double-dart injection might be possible, but the experiment and protocol have not been established yet.
Remote drug delivery system (RDDS) is commonly used by veterinarians to administer drugs to the unapproachable captive zoo and free-ranging animals. Although several commercial systems are available, they are expensive to purchase.
Remote drug delivery systems for administering anesthetic agents to free ranging wildlife must be appropriate for the size of the animal and the volume of drug to be administered. Many equipment systems are available for the remote injection of drugs, including high velocity dart rifles, low velocity systems and pole syringes. It is important to choose a system that will deliver the required volume of drug with the least amount of physical trauma to the animal (Bush, 1992; Kreeger, 1996). Hitting a proper injection site is critical when remotely injecting immobilizing drugs in wildlife species. A large skeletal muscle mass is usually the most desirable target to achieve an intramuscular injection. Regular practice sessions with remote drug delivery systems and knowledge of animal anatomy are necessary to be able to consistently hit the appropriate anatomical site. Factors such as season, age and body condition of the animal should all be considered before immobilization as they can radically alter the target site and the dose required. Additionally, an appropriate needle length should be chosen for the size, age and body condition of the target animal to allow effective injection and reduce the risk of laceration and trauma. High velocity dart rifles are capable of killing most mammalian species and should only be used by experienced personnel. They are generally much less accurate than traditional firearms. Most accidental animal deaths involving these firearms have resulted from using excessive velocity to propel the dart and/or missing the target area, causing penetration of a vital organ or body cavity, and/or broken bones. Low velocity systems, including CO2 powered pistols and low velocity dart guns, cause less trauma than high velocity dart guns because the projectile travels at a much lower speed. Low velocity systems, however, have limited use for most free ranging animals because they have a short range and are limited to smaller drug volumes. Slow-injection darts, pressurized with air or gas, cause less tissue damage when injecting than rapid-injection darts which contain an explosive charge. Pole syringes are useful for trapped or restrained animals. They are capable of delivering larger volumes of drug than some of the low-velocity systems and create less trauma than highvelocity systems due to the slow speed of injection. However, pole syringes can result in lacerations or needles can break off, especially when used with needles that are too long or when administering large volumes. Placement of the syringe needs to be accurate as pole syringes may harm the animal if incorrectly placed.
Darts
Several types of darts have been developed for remote drug delivery, two typical types are two-chambered compress gas darts and powder explosive powered darts. Two-chambered compressed gas darts are lightweight plastic darts with dual chambers divided by a movable syringe plunger in the centre , examples include blow darts and moulded nylon darts (West et al., 2014). Blow darts are constructed of lightweight medical-grade plastic and the sharp needle enables the penetration into various types of animal skin. Moulded nylon darts have heavier and made from moulded nylon, an opaque synthetic polymer, suitable for outdoors with long ballistic ranges. Powder explosive powered darts are heavyweight darts consisted of a powder explosive cap, a chamber for drug loading and a movable central syringe plunger to separate the drug from the explosive unit and trigger the mechanism . Many other darts have also been used such as chemical powered, spring powered, solid drug darts and biobullets .
Projectors
The selection of projectors for remote delivery system depends on the type of darts. The most popular type is compressed gas projector that includes blowpipes, blowguns, air and CO2 rifles and pistols. Blowpipes are the most versatile, economic and lightweight projectors available in the market. The key advantage of blowpipe is minimal trauma to the animal due to its low velocity (Kreeger, 1997; West et al., 2014). However, blowpipe requires practical experience and has limited effective range (about 0.5 to 10 meters) . Blowgun is similar to blowpipe but uses compressed gas to project the dart . This projector has higher accuracy, easier operation and longer range (about 5 to 30 meters) (Brockelman & Kobayashi, 1971; West et al., 2014). Air and CO2 rifles and pistols are a group of projectors with a barrel mounted onto a triggered compressed gas power, which are suitable for long-distance shooting as it may cause trauma at short range . There are other projectors appropriate for remote drug delivery, such as powder loaded rifles , crossbows, bows and injection collars .
Advantages and limitations of RDDS
Using a RDDS for wildlife delivery offers the following advantages: i) target specific; ii) dose tailorability based on the body weight; iii) various formulations can be administered; iv) short-distance contact with wildlife is avoided and v) economical cost per animal (Kreeger, 1997). However, there are still some limitations of current RDDS that need to be improved for the purpose of delivering contraceptive drugs: i) the formulations are limited to liquid or powder forms with a fast release of incorporated drug not suitable for longterm contraception; ii) recycling of the needle/syringe is difficult in the field and iii) dart size/shape cannot be customised based on animal species or projectors. To overcome the above shortcomings, this thesis aims to develop a novel BDDS capable of loading and delivering specific dosages of multiple drugs with both immediate and sustained release profiles to wild animals using biodegradable and biocompatible materials tailor-made in different shapes and sizes.
