Parasitology Control Programs PDF

PARASITOLOGY 5 Parasitology Control Programs Dr. Cassan Pulaski 21 August 2024 Learning Objectives: Students will be able to describe generic antiparasitic drugs classes commonly used in veterinary medicine (antiprotozoals, anthelmintics, insecticides, acaricides) with...

PARASITOLOGY 5 Parasitology Control Programs Dr. Cassan Pulaski 21 August 2024 Learning Objectives: Students will be able to describe generic antiparasitic drugs classes commonly used in veterinary medicine (antiprotozoals, anthelmintics, insecticides, acaricides) with emphasis on specific indications and selection. Students will be able to formulate control programs based on a knowledge of a parasite’s biology and the use of chemical and nonchemical methods of parasite control. Students will be able to develop a control or prevention plan to inform the client and/or public about the risks of major parasites (including biosecurity, zoonotic potential, and food safety). "White feet don't treat" ivermectin - some dogs with genes that cant have macrocytic lactones Treatment versus Control Anthelmintic treatment kills parasites May or may not control parasites Control implies the prevention of clinically and/or economically important levels of parasites and/or disease Strategic control of parasites involves the judicious use of anthelmintics, together with knowledge of the host, parasite, and environment and the properties of the drug being used Variation between small and large animals Zoonotic concern Production loss Can be difficult with cattle people. Horses - rotating protocol treatments based on time of year/seasonality/time of infections; don't treat at wrong time of year leads to increased resistance When we think about parasiticides, consider: What species am I treating? Can I use that drug in the species? Does it kill what I want it to? Are there any contraindications? Categories of Parasiticides Endoparasiticide – Kills internal parasites Ectoparasiticide – Kills external parasites Endectocide – Kills both internal and external parasites – New term coined specifically for avermectin/milbemycin (macrocyclic lactone) drugs Only ivermectins at the moment Categories of Parasiticides Antiprotozoals – Activity against protozoan parasites Anthelmintics – Activity against helminths (worms) Insecticides / Acaricides – Activity against arthropods (insects and/or arachnids) Antiprotozoals usually used as anthelmentics but effective against protazoa Fenbendazole - to treat giardia Anthelmintics Anthelmintics Major Classes: cattle horses – Benzimidazoles (fenbendazole, febantel, albendazole, oxibendazole) MOA: binds to beta-tubulin, disrupts polymerization of tubulin into microtubules (kills by effecting parasite's metabolism) Broad spectrum, safe, lots of resistance common first dewormer for foals – Macrocyclic lactones (ivermectin, moxidectin, doramectin, selamectin, milbemycin oxime) MOA: cause paralysis of pharyngeal & somatic muscles (can cause intestinal rupture with a drug that kills all worms at one time) Effective against most nematodes & arthropods, safe (note: IVM toxicity in dogs) – Membrane Depolarizers (levamisole, pyrantel) MOA: depolarizing NM blocking agents, spastic paralysis of worms (can cause intestinal rupture with a drug that kills all worms at one time) Broad spectrum nematocides, most very safe levamisole - narrow window TI; small ruminant use – Isoquinoline (praziquantel) Pyrantel - strongid MOA: ? Causes spastic paralysis of worms praziquantel effect doesn't translate to ruminants and flukes - doesn't Efficacy against cestodes, some trematodes, safe work well – Cyclooctadepsipeptides (emodepside) MOA: ? only one in the US right now New class Ectoparasiticides Control programs are individualized! Host-specific consider behaviors, ease of administration, where they live, etc. – Cats vs cows – Pets in a home vs shelter – Age, breed, reproductive status Consider environment, client/owner, goals – Housing, financial constraints, feasibility – Travel, animal’s job *Consider where each animal lives (i.e. Alaska vs. GA will have very different – Individual vs herd recommendations becuase of location) *CONSIDER FINANCIALLY FEASIBLE OPTIONS *travel - competition or breeding animals (stress risk and parasite risks of areas traveling to) Client-owned, small animals Testing check blood for microfilariae – Vector-borne parasite testing annually Heartworms (antigen + microfilariae in dogs) Tick transmitted pathogens (ex: Borrelia, Anaplasma, Ehrlichia) – Internal parasite testing AT LEAST annually Fecal diagnostics (flotation, PCR, coproantigen) Increase testing frequency in young animals, “risky” lifestyle frequency with young animals and risky life style - ie increased risk becuase of their lifestyle and habits Treatment – “Every Pet, All Year Long” other countries do more risk-based treatments (they don't recommend year-round prevention) US - year round recommendations – https://capcvet.org/parasite-product-applications/ – Test after treatment as well The future in small animal parasite control may look different… Drug resistance is increasing – Heartworm – Hookworm (Ancylostoma caninum) resistance now!! – Flea tapeworm (Dipylidium caninum) prazequantel resistance now Environmental health concerns, drug residues Risk-based recommendations – Spectrum of Care – https://petdiseasealerts.org/forecast-landing/ Large Animal (equine & production) Parasite eradication in every animal is impossible… – Minimize disease! Grazing animals WILL HAVE parasites - goal to minimize the disease Herd-wide control puts heavy selection pressure on worm populations for drug resistance (major concerns in large animal) – Maintain refugia (proportion of the worm population not selected by drug treatment) – Use drugs in combination *Use all at same time to treat - kill more parasites – Integrate non-chemical modalities Refugia example: Resistant Eggs and Worms Modified from Rose Nolen-Walston, DVM, DACVIM  Refugia Dilutes resistant worms so population stays susceptible 80/20 rule - small percentage are the highest shedders only target the ones that are most infected -- allows dilution factor because the resistant ones are not the only to survive Refugia Modified from Rose Nolen-Walston, DVM, DACVIM  Impact of Using Multiple Drugs on Efficacy (%) Drug 1 Drug 2 Drug 3 Combination *use drugs in combination to increase efficacy 80 80 96 and reach that effective dose 80 80 80 99.2 90 90 99 90 90 90 99.9 99 99 99.99 60 95 98 60 60 95 99.2 60 60 60 93.6 How do we keep balance? With a good parasite control program 1 2 3 4 5 Manage the Use anthelmintics Monitor and Quarantine and Investigate level of pasture properly treat the animals treat new treatment failure contamination selectively introductions Eliminate/minimize CLINICAL cases Minimize sub-clinical cases Some strategies to delay resistance Targeted selective treatment – FEC (only method for horses) targeted treatment – Diarrhea score based on weight gain - don't treat the ones gaining – Body condition score (also cattle) (they are healthy) – FAMACHA (best method for SR - Haemonchus)  Selective non-treatment (best method for cattle) – Treat only 80% or 90% of herd Leave heaviest or best-looking untreated Courtesy Dr. Fiona Kenyon, Moredun Institute, Scotland https://youtu.be/Zm41iJA1hrw?feature=shared Questions?