Internal Parasite Information Anne Oakenful– Diagnostic & Analytical Services – Oct 09
Internal Parasites • Internal parasites (worms and fluke) are estimated to be costing the Australian sheep industry $369m per year. • This cost includes mortalities and production losses (reduced wool cut, stained wool, lowered staple strength), as well as the direct costs of control (mainly drenches and labour)
Types of Internal Parasites • 4 main groups • Nematodes (roundworms) • Trematodes (fluke) • Cestodes (tapeworms) • Protozoans (coccidia)
Nematodes • commonly known as round worms eg: Haemonchus spp. (Barber’s Pole worm) Ostertagia circumcincta (Small Brown Stomach worm) Trichostrongylus spp (Black Scour worm). • by far the most economically important group of internal parasites
Life cycles…. Nematodes • Most common internal parasite of domestic livestock • Naturally carry low worm burdens • Animals need to be exposed to develop resistance • Become a problem when numbers increase to cause production losses and or animal have other diseases
Barber’s Pole Worm • quite large worm (20 to 30mm) found in the abomasum. • Adult females have a characteristic barbers pole appearance like red and white twisted wire. The male is smaller (around 15mm) • sucks blood from the lining of the stomach which causes anaemia. • adults suck around 0.05ml of blood per worm. A burden of 1000 worms may remove 50ml of blood (egg count would be around 5000epg) • Sign of heavy infection include • lack stamina, pale gums and conjunctiva, bottle-jaw, constipation. • faecal worm egg counts are usually high before symptoms show (could be over 10,000 epg). • a subclinical (no visible signs of worms) infestation can reduce weight gains by 30%, wool growth by 10% and milk production by 30%. Information sourced from Wormboss .com.au
Brown Stomach worm • occurs in most sheep areas of Australia and is a major parasite in winter rainfall districts. • small (10mm) red-brown worm just visible on the lining of the abomasum. • very resilient, can survive freezing on the pasture and dry conditions. • adults can arrested or inhibited for varying lengths of time • Adult female brown stomach worms lay 50 - 100 eggs per day. • damage the lining of the stomach as they mature from larvae to adult worms. • heavy infections cause rapid loose of condition, profuse scours occasionally death. • animals with fewer worms are unthrifty and daggy. • Mixed infections of brown stomach worm and black scour worm are more lethal than infection with only one of the worms. • Infection caused whitish nodules on the abomasum lining. • production-loss occurs in the absence of obvious disease. • a subclinical infestation can reduce weight gains by 35%, wool growth by 20% and milk production by 20%. Information sourced from Wormboss .com.au
Black scour worm • Black scour worms occur in all sheep production districts of Australia. • Adult female black scour worms lay 100 – 200 eggs per day. • Black scour worms live in the first three metres of the small intestine of the sheep and cause damage to the lining of the gut. • the larvae burrow into the wall of the small intestine and undergo a moult to become an immature worm. • heavy infections cause rapid lose condition, scours, which may be black. The animal can dehydrate and may die. • A subclinical infestation can reduce weight gains by 35%, wool growth by 10% and milk production by 20%. • Damage to the intestinal wall leads to problems with nutrient absorbtion. Information sourced from Wormboss .com.au
Trematodes • include Fasciola hepatica (liver fluke) and Paramphistomes (stomach fluke). • The most economically important fluke for livestock is liver fluke. • This parasite causes substantial economic lost in certain geographical areas in Australia.
Life cycle… Liver fluke • Cost sheep and cattle industry around $50-80 million a year • Reduced production and quality of wool • reduced lambing percentages • Poor growth rates • Reduced milk production • Have indirect life cycle that relies on freshwater snail (lymnaeid snail) as intermediate host. • Infection only occurs where snail is found
Life cycle… Liver fluke cont... Adult flukes in bile ducts Metacercariae ingested Fluke eggs in faeces Metacercariae on vegetation Lymnaeid snail (intermediate host) Miracidia Cercariae leave snail sporocyst cercariae rediae
Life cycle… Liver fluke cont... Diagnosis • Faecal sedimentation test • Only detects adult infections producing eggs • Blood ELISA • Very reliable • Detects infection from 4 weeks
Protozoans • Coccidia can affect all domestic animals. • Most are host specific. • Eimeria is the main coccidia infecting sheep and cattle. • Cryptosporidium is another protozoan that can affect sheep and cattle.
Life cycle… Coccida • Generally host specific • Cause disease by invading cells of intestinal wall • Can be present in low numbers with no ill-effect • Animals develop immunity as they mature • Immunity levels can drop if under stress (overcrowding, nutritional, weaning etc)
Life cycle… Coccida cont… • Common signs of infection • Diarrhoea (severe and containing blood) • Rough coat • Poor weight gain • Weight loss • Weakness • Lower milk/meat/fibre production
Life cycle… Coccida cont.. Coccidia multiply in intestine and form new oocysts (10 days approx.) 24-48 hours in summer May take weeks in winter Oocysts in droppings Infective oocysts
Life cycle… Coccida cont.. • In cattle infection called ‘black scours’ • Profuse, dark, foul smelly diarrhoea • Animals infected by • Contaminated food, water or bedding • Licking contaminated hair or udders
Life cycle… Coccida cont.. • Reduce infections by: • Using feed and water troughs • Reduce overstocking, especially on damp pastures • Avoid holding animals in yards for long periods • Avoid mixing young and old stock together
Faecal Egg Counts • Is the most routinely performed test to estimate the worm population in an animal. • Strongyle eggs float in saturated solutions of salt. • If you use known quantities of samples and reagents, the number of parasite eggs per gram of faeces can be determined
Collecting the sample Samples collected from : • The ground - holding the animals in the corner of a paddock for 5-10 minutes and allowing them to drift away • Directly from the rectum - insert gloved finger into rectum and gently move finger around until faeces is released. (should happen within 30 seconds)
Wormtest kits • Are a valuable tool for worm control • Can be used to • Monitor worm burdens • Determine if a drench is require • Determine if the drench used was effective (drench resistance) • Determine how “worming” a paddock is • Determine the species of worms present in the animal (if worm type conducted) • Base management decision on results
What happens in the lab • Weigh out known sample amount and add saturated salt solution • Subsample loaded into special chamber and then eggs are counted under the microscope. • Results are multiplied by 40 to give the number of eggs per gram of faeces (epg)
Identifying Eggs • Strongyles have a number of species that produce eggs of the same relative size. • Need to hatch the eggs to identify larvae
New Dipstick test • Australian Sheep Industry CRC have developed the dipstick test to detect when sheep should be treated to prevent Barber’s Pole worm disease (haemonchosis) outbreaks • Can use the test in conjunction with faecal egg counts • Test gives results before worm egg counts rise as immature worms are detected a week before they produce eggs
Dipstick Test cont… • The basis of the test is that Barber’s Pole worms are blood-sucking internal parasites. As they feed on the abomasum some blood passes through the digestive tract. • The test detects haemoglobin (a product of blood breakdown) and changes colour according to the amount of blood in the sample
Dipstick Stick cont…. • Major benefits include: • Results are available within 30 minutes on farm • Burdens are detected before egg production begins • The test is easily accessible and able to be kept on hand • The test is reliable, accurate and inexpensive
Dipstick Stick cont… • In warmer months the dipstick test can be used weekly to predict risks • Training days for users will be conducted in coming months • At present the test is only been evaluated for sheep • Interested graziers should contact their local Merial or Ancare Territory Manager or their local reseller for further information
Egg Count Result Interpretation • It is very difficult to give hard and fast rules on interpreting egg counts • There are so many variables to consider including: • age of the animals • physiological status • host species • nutritional status • forecasting • management factors • the worm mix
Age of the animal • Adult dry animals in good condition tolerate worms much better than young or poor animals. • In the case of extensively grazed cattle, adults often require little or no drenching - except where liver fluke is a problem. • Young animals, up to two years of age, are likely to need more frequent drenching
Physiological status • Late pregnancy or lactating animals have a temporary relaxation of immunity • it may be appropriate to consider drenching at lower egg counts than otherwise.
Host species • Host immunity will have a bearing on the interpretation of egg counts. • Well-grown cattle and sheep over two years of age develop some immunity to worms. • The immunity in cattle tends to be stronger than in sheep. • Goats do not appear to develop a great deal of immunity, even when they reach adulthood.
Nutritional status • Well-nourished animals quickly develop a strong immunity to worms • withstand a worm challenge better than poorer animals • moving animals onto a better pasture, or hand feeding can, in some cases, have the same effect as drenching
Forecasting • A decision to drench or not, based on a certain egg count, may be influenced by how wormy pastures are likely to get in the coming weeks and months. • plans for a move to cleaner, better pasture will impact on the decision to drench.
The worm mix • if barber’s pole worm is a common problem, egg counts are likely to be higher. • of the three major sheep worms, barber’s pole worm has the highest egg output (around 10,000 eggs/day), followed by black scour worm (100-200 eggs/day) and then small brown stomach worm (50-100/day).
Guide to worm egg counts in sheep The department has a Primefact that gives guidelines for result interpretation. As a rough guide: • 0-200 epg –low • 200-500 epg – moderate • 500-1000 – high Remember to • Check egg counts in 4-6 weeks after significant rain, or before a ‘management event’ e.g. summer drench, pre-lambing, prior to yarding, or when there are signs consistent with parasitism. • animals can get a heavy worm burden quickly before egg counts rise.
Control Options for Internal Parasites When designing control program need to take into account • Available land • Range of animals involved • Limiting restraints eg pasture • Environmental conditions
Control Options for Internal Parasites The 4 main components are: • Strategic drench management • Grazing management • Nutrition of the animal • Breeding for worm resistant animals (in sheep)
Strategic Drench Management • Drenches divided into classes based on main active component • There are broad and narrow spectrum drenches • Need to rotate between classes to minimise development of resistance
Strategic Drench Management cont… Broad spectrum • Effective against wide range of parasite species & include: • Benzimidazole (BZ) or ‘white’ • Levamisole (LEV) or “Clear” • Macrocyclic lactone (ML) includes the avermectin (ivermectin/abamectin) and milbemycin (moxidectin) sub-groups. • Naphthalophos (NAP) or OP (organophosphate), often used in combination with white and clear drenches Narrow spectrum • Only effective against one or two parasite species • Closantel which has sustained activity against susceptible barber’s pole worm, and strains of liver fluke. • Triclabendazole which is highly effective against mature and immature stages of susceptible strains of liver fluke.
Strategic Drench Management cont… Multi-combination drenches • Recent developments with 3 (eg TritonTM ) or 4 (Q-Drench TM)components. • May be used where resistant worms are known to be present. New Drench on the Block • Zolvix is a short acting broad spectrum drench • Developed by Novartis • Belongs to a new drench group AADs (amino-acetonitrile derivatives) • First new drench family since 1988 • Not yet available in Australia – may a few years before released here
Strategic Drench Management cont… • Get the most out of each drench by: • Choose the correct drench for the job • Get the dose right (to heaviest in mob) • Calibrate drenching equipment • Deliver the dose correctly • Fasting before drenching (do not do this with clear or rametin based drenches)
Strategic Drench Management cont… • Effective drench kills 95% or more of worms. • Important to know your drench resistance status • Can check by • Quick Drench Check • Drench Test
Strategic Drench Management cont… Drench Resistance in Sheep in NSW
Strategic Drench Management cont… Sheep • Strategic worm programs designed for sheep producers in NSW • DrenchPlan • WormKill • WestWorm • FarWestWorm • aim to reduce the number of drenches and worm larvae on the paddocks and to minimise production loss. • Wormboss program • Australian Wool Innovation and the Sheep CRC • has information on all aspects of sheep internal parasites • has an interactive component “Ask the boss” to provide interactive advice.
Grazing Management Prepare “low worm-risk” paddocks • have relatively lower levels of infective larvae than other paddocks. • use for most vulnerable animals i.e. weaners, pregnant/birthing animals. • achieved by grazing with another animal species • most worms are host specific - ingestion by the non-preferred host results in the death of the larvae. • Exception is barber's pole worm and stomach hair worm (T axei) which can infect both sheep and young cattle. Therefore, the use of adult cattle for cross grazing is preferred.
Grazing Management cont… • The length of time needed to graze paddock to help clean off infective larvae will vary from region to region and also depend on seasonal conditions. • If running one type of animal - use older dry animals to graze the paddock (higher immunity). • If the sheep are treated with a fully effective short acting drench, they can be used to "clean" paddocks for weaners (smart grazing) for the 21 - 28 day period without fear of recontamination of the paddock.
Grazing Management cont… Spelling a paddock • may be viable in some situations. • the length of time needed will vary depending on • seasonal condition • length of pasture • type of worms present. • short-term spelling is of little use for worm control • studies have shown that spelling for more than 10 weeks in autumn/winter is needed to have a useful reduction in worm larvae numbers.
Grazing Management cont… Cropped paddocks • summer crops, such as lucerne, provide high nutrition to help the animal fight off worm infections. • very good for young and susceptible stock • help to break the worm cycle as generally have very low worm larvae contamination levels. • But these paddocks can help to select for worm resistance. • If the animals are drenched when going onto the paddock, the only worms left in the animals will be those resistant to the drench used. If animals left on paddock for more than 30 days any eggs/larvae deposited on the paddock will be a resistant strain. • It is important to keep this in mind when making future management decisions involving the paddock.