- - AGRICULTURE CORE CURRICULUM - - (CLF3000) Advanced Core Cluster: ANIMAL SCIENCE (CLF3350) Unit Title: LIVESTOCK PESTS ____________________________________________________________________________ (CLF3352) Topic: EXTERNAL PARASITES Time Year(s) 4 hours 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (F-2) - Draw the life cycle of at least three common external parasites including the possible hosts and methods to control each parasite. (F-5) - Describe production problems associated with the housefly, blowfly, botfly, and horsefly and explain two methods in which these can be controlled. Special Materials and Equipment: Insect collection and slides containing examples of lice, the blowfly, the botfly, and the horsefly. Samples of pesticides used on livestock and their containers. Plenty of blank paper and colored pens and pencils. References: Ensminger, M.E. THE STOCKMAN'S HANDBOOK. Metcalf, C.L. DESTRUCTIVE AND USEFUL INSECTS. Evaluation: Quiz by instructor and evaluation of parasite lifecycle drawings. TOPIC PRESENTATION: External Parasites A. Life Cycles and Control of External Parasites 1. Cattle lice a. Types -- There are two : 1) Biting lice (little red louse): a) live on a host and infest other animals by contact. b) are most abundant during the winter when the hair coat is thick. c) The eggs are white, barrel-shaped objects, glued by one end to a hair or a strand of wool. d) The young louse (nymph) hatches within 1-3 weeks depending on the weather, and looks like the adult except smaller. An incomplete metamorphosis takes 3-5 weeks within the entire cycle. e) When the coat is shed in the spring, the lice seem to disappear, but enough remain to carry the species over until favorable conditions permit them to increase again. 2) Bloodsucking lice (short-nosed cattle louse): a) Are most abundant during the winter. b) The skin will show dark-blue patches which looks some- what like dirt, these are actually clusters of lice. (Pretty gross, huh?) c) The eggs are glued to the base of the hairs by one end. d) All lifecycle stages are spent on cattle and are similar to biting lice. b. Hosts - since lice are species specific so each type of animal has its own particular type of lice. However, 1) some types of lice will survive on animals other than their hosts for short time periods, and 2) the lifecycles for all lice are similar. c. Control: 1) Avoid overcrowding of animals since lice are spread by contact. 2) Good nutrition helps animals resist infestation (lice are most prevalent on poorly fed, malnourished animals). 3) Sprays are most practical since all parts of the body can be contacted. 4) Dips are used in large scale operations to control all types of external parasites including lice. 5) Dusts - are inexpensive, but practical for small scale operations; however, reapplication is usually necessary. 6) Shampoos, pour-ons, and spot-ons can also be used, but are not practical for working with large groups of animals. 2. Sheep ked (Sheep-tick) a. Lifecycle: 1) The sheep ked is one of the most remarkable insects known because of its method of reproduction. a) It is not really like a tick, which drops to the ground to lay eggs, but rather a wingless fly, spending its whole life on the animal. b) Two life stages are commonly found on sheep at any season of the year. c) The adults are brown, wingless, and six-legged and live on the skin all over the body. They live in higher concentrations in certain areas on the animal. d) The other stage is a chestnut-brown, seed-like object that is glued to the wool on the neck, thighs, and belly. e) The sheep ked does not lay eggs but gives birth to a maggot which then attaches to the wool and becomes a pupa. f) The pupal case enclosing the larva of the insect will emerge from the pupa as an adult. b. Sheep are the only host for this parasite. c. Control is a accomplished through.insecticide sprays which are most effectively used during shearing. 3. Mange Mites (Sarcoptic Mange) a. Lifecycle: 1) Mites burrow beneath the skin on the less hairy parts of the body. 2) Females mate and lay their eggs within the tunnels in their burrow. 3) The young mites hatch within 10 days and also start to burrow beneath the skin. 4) All stages of the mite secrete a very irritating toxin which causes the affected animal to scratch constantly. 5) They are most common during winter. b. Hosts vary and include man, horses, hogs, dogs, cats, rabbits, sheep, and cattle. 1) Each is attacked by a different variety of the same species.. 2) The subspecies will not cross-infect other hosts. 3) Animals are infested by contact with others of their own species. c. Control: 1) Mange is very contagious. a) Isolation and quarantine of infected animals is the most important control. b) Some species or areas require cases to be reported to public health officials. 2) Dips are very effective in controlling mites since all parts of the body are contacted by the pesticide. 3) Sprays are effective if used with a high pressure spray system since all parts of the body need to be contacted with the pesticide. (The spray must penetrate the hair all the way to the skin.) 4) Injections, and Shampoos are also useful. B. Production Problems Associated with Flies 1. Housefly a. Causes problems by: 1) serving as intermediate hosts for roundworms in horses. The worm eggs transfer to sores or to the lips and eyes of horses. 2) serving as intermediate hosts for tapeworms in poultry. When birds eat flies or maggots that are carrying tapeworm eggs. 3) annoying animals by landing on the skin -- which may reduce rate of gain of high level of activity due to the irritation and distraction. b. Control: 1) involves properly disposing of materials which serve as food and habitat (break the life cycle) for the house fly. These include: a) manure, b) organic waste, and c) dead animals. 2) Sprays offer temporary control; however, ALWAYS follow label instructions since these applications may be toxic to livestock. 3) Baits provide longer term control than sprays are messy, and the dead flies must be cleaned up. 2. Blowfly a. Causes problems by "fly-strike", the blowflies lay eggs around wounds such as those caused by dehorning, castration, scratches from fighting, or the navel cord in newborn young. 1) The flies deposit eggs that hatch. 2) The maggots (larvae) feed in the wounds and invade healthy tissue, and the larvae drop out and pupate in the soil. 3) Wounds do not heal and eventual death may result. b. Control: 1) Prevent all excess breaking of skin or flowing of blood when castrating, dehorning, branding, and the docking of tails during the warm season of the year when flies are most active. 2) Introduction of sterile flies in an infested area. 3) Treat all wounds immediately with a fly repellant and reapply the treatment at specified recommended intervals. 3. Botfly a. Causes damage by: 1) annoying horses with its loud buzzing. 2) laying eggs on the hairs of the legs, chin, or nose. a) These eggs then hatch and the larval stage (10 months for this stage) migrate down the mouth and live in the digestive tract of the horse during the winter. b) The eggs are stimulated to hatch by the horse licking them. c) The larvae pass through the feces in the spring, burrow into the soil, pupate, and then emerge as adult flies in the late summer. 3) injuring or perforating the stomach (during the larval stage). b. Control: 1) Pasture animals at night during fly season, since bot flies are only active during the day. 2) Use a warm sponge to remove eggs from legs and belly. Since eggs hatch with a sudden rise in temperature this removes the larva as they hatch. 3) Use of anthelmintics such as Zimectrin, which contains ivermectrin, before the final fall freeze to the internal larval stages. __________________________________________________________ ACTIVITY: 1. Have students draw the lifecycles of the external parasites studied in class, use colored pencils and pens. 2. Have students learn to identify the insects studied using slides or insect collections. 3. Observe samples of pesticides commonly used on livestock. __________________________________________________________ 5/10/90sg #%&C