Worms are Winners, Why?

» Parasites are organisms that live in or on a host and in general do nothing to help the host live better lives

» It is not in the parasites best interest to harm the host; which provides nutrition, protection and a place to hang out

» Disease occurs when the number of parasites is in excess of what the host can tolerate

» Generally speaking, gastrointestinal nematodes, and coccidia are the most important parasites of small ruminants, locally flukes or meningeal worm may be extremely important

» Haemonchus contortus: stomach, barber pole or candy cane worm

» Trichostrongylus colubriformis: black scour or bankrupt worm

» Nodular worm, Tapeworms: in 2015 more annoyance than disease

» Flukes, brain worm, devastating or not present

» Adult worms live in host, larvae in pasture

» Eggs produced by adult worms passed in feces, the eggs hatch and the larva feeds on bacteria in feces

» Larva requires a week to a month from when the egg is passed in feces to become infective

» Larva escape moistened feces and are then grazed from vegetation

» Rain allows escape from feces, dew allows larvae to ascend vegetation

» Worms are transmitted when larvae ascend vegetation in rain water, dew etc. then they are grazed

» Larvae actively wiggle in water to move but this expends energy

» They do not move in the dry fecal pellet

» They die because it’s too dry, too long or they had too many wiggles

» Life span: outside the host, 1 month warm wet summer, >8 months cool or dry season

» Larvae survive in pasture during drought in fecal pellet or soil or as arrested larvae in host

» Climate; determines the species of parasites in a geographic area

» Weather; determines when the parasites are transmitted: Two inches rain for development and escape

» Management; determines who and when hosts are going to be exposed to parasites

high rainfall >32 inches annual rainfall, parasite paradise low to medium >16 inches, few parasites very low rainfall depends on range, few if any

Transmission of nematodes in west central Texas

» 2011: dry as a desert NO WORMS few coccidia » 2012: rained some few worms autumn » 2013: rained a bit more and the drugs did not work » 2014; Mild moist winter

Dry mild spring Rain early summer Disease July August

» 2015: rained, rained, rained, during the spring early summer coccidia and Haemonchus bloomed but the sheep and goats did not. Dry again little transmission until it rains??

» Most important parasite of small ruminants in Texas

» Warm season parasite; transmitted April through November

» Cause anemia due to blood sucking, they can remove more blood from a sheep or goat than a knife applied to the carotid arteries

» There is a direct relationship between the severity of disease and the number of worms in the stomach

» Disease due to blood loss death can occur per acutely; animals drown in their own fluids

» Disease: anemia, and hypoproteinemia (bottle jaw)

» Tremendous fecundity 5,000 or more eggs / female / day

» Sheep or goats are genetically programmed to develop / or not resistance to specific worm species

» Immunity acquired by exposure to infective larvae

» Immunity wanes at parturition which coincides with reactivation of arrested larvae

Haemonchus contortus

» Overwinters in abomasum as arrested larvae

» Emerges at parturition or when new forage is grazed

» Usually numbers of larvae becoming adults is below threshold for disease but contamination of spring pasture important

» Impaired immunity in early lactation or when young are nibbling forage larvae from pasture establish

» Numbers of worms increase quickly in spring

» Cool season parasites; mild wet winters, spring and autumn if moist but can be transmitted year around

» Small intestine parasite » Interferes with absorption of calcium, phosphorus,

vitamin D; possibly causing rickets, abdominal pain » Diarrhea, poor weight gain » Depressed appetite » Most disease seen from weaning until a year of age » Egg looks the same as Haemonchus

» Oesophagostomum Nodular worm adults live in large intestine

» Larvae are entrapped in wall of intestine in pus filled nodule which will calcify in time

» Life cycle outside of host similar to Trichostrongylus except nodular worms can penetrate the skin as well as being ingested

» Economic loss: value of intestine at slaughter, lowered reproductive potential, diarrhea, poor doing animals

» Most of our modern drugs very effective against adult worms

» Larvae in nodules in mucosa emerge in 7 – 10 days susceptible host

» Larvae remain in nodules for up to a year in host with resistance to the worm

» Bacteria in nodule adversely affect host

» Brain worm cause problems in nervous system from abnormal gait to an inability to rise

» Larval worms travels through spinal cord and brain

» Brain worm; east Texas hardwood forest need white-tailed deer and snails on vegetation, worm transmitted by eating snail

» Possibly in eastern hill country of Texas

» Flukes only important if you have them; only a few ranches in hill country and west Texas have the snail host which lives in shallow water

» The snails are common in coastal plain and up major rivers

» Common fluke really hard on small ruminants, but it only takes one deer fluke to kill a sheep, goat or alpaca

Common fluke Deer fluke

» White-tailed deer transmit several parasites which can be devastating to competitors: Parelaphostrongylus tenuis Brain Worm Fascioloides magna Deer Fluke Haemonchus contortus Barbers Pole Worm Ixodes scapularis Deer tick Amblyomma americanum Lone Star Tick Dermacentor variabilis American Dog Tick

» Tapeworms are disgusting: » Moniezia lives in intestine is up to six foot long. No damage

proven to be caused by the tapeworm. It requires small mites on forage as the intermediate host

» Infection with Moniezia is associated with enterotoxaemia due to changes in the environment in the small intestine allowing the proliferation of the bad bacteria; vaccinate kids and lambs

» Thysanosoma ,in Texas west of Colorado river, a tapeworm that lives in bile ducts will cause condemnation of liver

» A small insect (book louse) on forage is the intermediate host.

» Associated with Klinegrass toxicity; toxins are normally excreted in bile

Moniezia expansa tapeworm sheep, goats

» Breed and use of sheep or goats

» Pasture or confinement

» Interactions with other animal species

» Quality and quantity of feedstuffs

» Season of parturition

» Age of weaning

» Source of livestock and parasites

» Use of anthelmintics; which drug(s) and when

» Breeds develop resistance to the parasites in the environment in which they originated

» 20% of flock produce 80% eggs

» Resistant sheep or goats must be exposed to parasites to become immune to disease

» Young do not acquire immunity until 2 to 4 months of age

» Resistance wanes when prolactin levels rise (parturition i.e. lambing or kidding)

» KILLUM ALL! » Maybe not? » Control disease, live with the parasite » Parasites, like bacteria, have evolved to become

resistant to the chemical agents that were very effective against them

» Parasites stimulate a protective immune response by host if no exposure no protection

» Protection is from disease not infection so healthy animals still have parasites

» Anthelmintics are drugs which are labeled to kill worms

» Mainstay of parasite control for past 60 years

» Many species of worms no longer economically important

» Less reliance on avoiding parasites more on killing them

» Haemonchus large genetic base and is able to exploit changes has become resistant to all of the anthelmintics used in North America

» Resistance by Haemonchus contortus common especially in goats and sheep

» Resistance by Trichostrongylus rising

» Increased use of anthelmintics leads to drug resistance

» Haemonchus resistant to all classes of drugs

» Resistance must be tested at each farm

» Nothing yet!!

» Monepantel (Zolvix) a drug now used in Europe, Australia and New Zealand under evaluation in US for use in sheep!

» Appears to be effective against most worms resistant to other classes of anthelmintics

» Will probably get approval for use in sheep in the U.S. by sometime in 2014, no , 2015?, 2016?

» Rotation of anthelmintics: A well conceived idea that makes sense unfortunately wrong!

» Treat only heavily parasitized animals

» Allow susceptible worms from refugia (a population of worms not exposed to anthelmintics) to mate with resistant worms

» Remove susceptible hosts from population

» Management to minimize use of anthelmintics; by lower exposure of susceptible hosts to worms

» Only use effective drugs

» Buy worms; come wrapped in a sheep, goat, alpaca, calf

» Treat to keep levels of parasitism at lowest levels possible by attempting to eradicate worms

» Do not allow stimulation of the immune system by treating more than necessary preventing moderate exposure

» Under dosing; dosing for the average weight, injecting anthelmintics with residual anthelmintic

Be careful of what you buy

You Might Get Something You Had Not Intended!

» Increased protein intake increases immune responsiveness, especially at parturition: this may be expensive or difficult to ensure consumption by the at risk animals

» Copper oxide wires; kills Haemonchus, also sheep if extreme care is not used, If used judiciously may be excellent control

» Nematophagous fungi show promise as feed through or rumen bolus to kill larvae in feces not in sheep

» Diatomaceous earths in feed may lower survival by killing newly hatched larvae through desiccation in fecal pellet, no killing in sheep and not effective in humid areas

» Botanical anthelmintics are generally found to be locally effective, ineffective or unsafe

» Condensed tannins; Polyphenolic compounds enhance protein digestion not only kill worms but improve nutritional status (bypass protein) examples Quebracho, Sainfoin, Chicory, Birdsfoot trefoil and Sericea lespedeza hay or grazed

» Juniper terpenes; Effect of plant products or behavior of animals eating juniper seedlings? apparently both! Feeding juniper appears to be both nutritional and deleterious to worms

» Goats and deer are naturally highly selective browsers, not grazers

» Sheep, cattle and horses grazers

» Worms have a problem in getting more than a few inches off the ground

» Taller nutritious palatable forages are preferred by browsers

a worm free pasture

Selective use of forage may increase nutrition and lessen worm problems

Browsing keeps away from worms

» Summer perennial grass (coastal bermudagrass) is the perfect forage for the propagation of Haemonchus contortus

» The temperature and rainfall ideal for grass growth is ideal for Haemonchus

» Use summer grasses after cutting hay or grazing by adult cattle to dilute worm population

» Move immediately after a rain to evade the larvae exiting the fecal pellets

» Shared grazing; Each species of grazing animal has its own preferred forage more pounds of livestock can share a pasture without putting undue pressure on the environment and dilute the exposure to parasites

» Rotate between classes of livestock: Susceptible animals graze followed by resistant animals harvesting larvae from pasture; fewer larvae available when susceptible animals return to pasture

» Prescribed burning of pastures will expose worms to drying, lowering parasite numbers

» Moving animals on to rested pastures lowers the exposure to parasites

» Short duration pasture rest will result in high quality palatable forage but will result in greater exposure to nematode larvae

» Move after 30 days in wet summer conditions with rapidly growing forage but over seeded rye grass or dormant grass; worms survive at least 8 months

» Tilled small grain or annual pasture; no worms

» A population of worms not exposed to anthelmintics: a) on pasture b) in the host, metabolically inactive c) in host not treated

» If worms are not eradicated a refugia becomes important as worms surviving treatment are probably resistant

» Refugia worms enter hosts and mate with resistant worms diluting resistance genes

» There are no susceptible worms in refugia on many farms in 2016

» Each farm is an ecosystem it has its own population of hosts and parasites as well as its unique biota, soil, weather and management

» Anthelmintics are as effective as the worm population to which they are exposed are susceptible

» Feed salesmen, county agents, veterinarians or professors don’t have a clue unless they have evaluated the parasites on the farm

» Allow exposure to moderate numbers of worms to stimulate protective immunity

» Selection of individual animals with the genetic capacity to tolerate or lessen establishment of worms

» Genetic selection for the environment in which small ruminants live not for maximum productivity under ideal conditions