In formulation chemistry, compounds are mixed to get a product with the desired characteristics. Examples of formulations are adhesives, paints, inks, cosmetics, detergents, pesticides and pharmaceuticals. Depending upon what a product is needed for and how it will be used or applied, needed qualities may include adhesiveness, weather resistance, correct texture, long or short shelf life or stability, biodegradability, specificity and attractiveness. Some of these properties (or the correct level of these properties) may not be inherent in an original product and must be added by changing its formulation.
One of the most difficult problems faced by formulation chemists at NWRC is finding a way for products (vaccines, baits etc.) to be delivered orally to wildlife species. This delivery method is desired due to the fact that wildlife species are much more inaccessible than livestock or companion animals.
In some cases, compounds used by NWRC are proteins which, once ingested, are recognized as food by the body. Stomach acids will then be secreted, destroying the active ingredients before they can act. One way to ensure compounds aren't destroyed in an anima's stomach is to encapsulate them (enclose them in a capsule). These encapsulated formulations are protected in the rumen and stomach and later release the active ingredients in the small intestine to increase absorption. In another example, active ingredients have been incorporated into a synthetic grit matrix to develop a species-specific controlled-release formulation for management of pest birds. Following ingestion of the grit formulation, the active ingredient is released as the matrix is slowly worn down in the crop of the bird. Controlling size of grit pieces offers a means to decrease ingestion by nontarget birds.
Below are other instances in which formulation chemists have contributed to products developed at NWRC.
Alpha-chloralose is a narcotic that, when used in concentrations of less than 2.5%, can anesthetize birds for removal from a location but not kill them. In early days of use, alpha-chloralose was mixed with butter and squirted into bread for delivery. A more easily produced and delivered product was needed. Tests were completed to determine how much active ingredient was necessary to achieve the desired effect in target species. Formulation chemists then produced an alpha-chloralose tablet with the active ingredient held together by a binding agent (common binding agents are lactose, microcrystalline cellulose, etc.). The tablet also had to have properties that allowed it to dissolve in water so the alpha-chloralose was available for ingestion. Formulation chemists added color to the tablets so that field operatives could distinguish the 3 different strengths of the product.
Oral Rabies Vaccine Development
Tetracycline is a compound that is employed as a biomarker in vaccines or other orally delivered products. By looking for tetracycline in animal tissue samples (primarily teeth and bones), scientists can determine whether the target animal populations are ingesting the associated vaccine. For example, tetracycline is used in rabies vaccines. Because some animals, such as skunks, don't like the taste of tetracycline, formulation chemists had to find a way to to mask its odor. Additionally, baits used for larger animals like raccoons weren't useful for skunks because the skunks often nibbled only around the edges of the bait, not swallowing it. The vaccine dose, in the middle of the bait, didn't get delivered. Thus, the tetracycline was re-formulated as small particles layered with a taste-masking coating and applied directly to the vaccine sachet (a plastic envelope with the liquid vaccine inside), yielding much higher bait take and improved correlation between marking and identifiable levels of antibodies to the vaccine.
DRC-1339, an avicide registered for use on some bird species, has been an extremely difficult problem because of the reactivity of the molecule (with light, air, etc.). DRC-1339 comes from the manufacturer as a powder. To be used as part of a rice bait, it must be formulated with an adhesive to stick to the rice. Unfortunately, the developed bait turns orange when used in the field, and birds won't eat it. Attempts are being made to alter rice properties so it doesn't react with DRC-1339 (for example, oxidizing it).
To trap the brown treesnake, an invasive species on Guam, live mice are used as baits within the live traps. These mice are separated from the main portion of the trap and cannot be actually be reached by the snakes. To sustain the mice for long periods of time, potatoes are placed in the live trap as a source of moisture for the mice. Grain bait blocks are also placed in the traps to provide food. Because potatoes had to be shipped to Guam, and people had to be hired to make the bait blocks, NWRC chemists were asked to develop a more efficient way of providing sustenance for the mice. The chemists were able to formulate a new product with a Konjac matrix (Konjac is a water-swellable dietary fiber used as a thickener and stabilizer) that held water and grain together as a one product, thus improving trapping procedures.
The M-44 is a mechanical device that, when triggered, expels cyanide. Canids are lured to the M-44 by the use of odor attractants. Initially, individual trappers were mixing their own variations of attractants. These users, however, wanted a more uniform and easily reproducible attractant, so NWRC chemists developed a product that, while attractive to canids, minimized nontarget impacts. The lure was composed of gelatin (regular Knox gelatin) and Konjac (for a binding matrix) glycerin, and some corn oil (to better hold odors).
Melting of baits was another problem to be solved. The bait was developed so that it was more thermally stable and could be used in warm climate states such as Texas as well as cooler areas such as Wyoming.