Internal Parasites of Dairy Cattle

C. H. CourtneyUniversity of Florid aGainesville, FL f//

The two most important parasitic diseasesof dairy cattle include parasitic gastroenteritis(disease caused by stomach and intestinalworms) and coccidiosis . Less important but stil lan occasional problem are lungworms and liverflukes. Whereas parasitic gastroenteritis an dcoccidiosis are likely to be a problem on mos tlarge dairies, lungworms have been nearlyeradicated by modern wormers and liver flukesoccur only in limited areas of the US.

Parasitic Gast roente ritis (PGE)

This is a condi tion characterized by weightloss, poor growth, loss of appetite, diarrhea,bottlejaw, and anemia in heifers during thei rfirst season on grass . PGE is caused prima ri lyby the Brown Stomach Worm (Ostenagiaostenagi), Barber's Pole Worm (Haemonctucsplacei), Bankrupt Worm (Trichosrrongylus arei) ,and several species of Coopers Worms(Cooperia oncophora, Cooperia punts= andothers) .

Seasonal Patterns of Parasitism. NorthernUS: as a general rule, worms are a summer/fallproblem in the northern and midwestern states .Worm eggs shed on pasture in spring developto infective larvae by July, and high levels o fpasture infectivity persist through the fall .Overwintering is a problem for these parasites .HaemoncJuct, Ostenagia, and Cooperia areshort-lived as adult worms (30 to 50 days), an dthey survive the winter as dormant (arrested ,hypobiotic, or inhibited) larvae in hosts thatmature and commence egg laying in spring.Onset of cold weather in fall conditions causesinfective larvae on pasture to undergo arrestwhen ingested rather than develop straightaway

FLo«io,DAIRY CHECK-OF F

to egg-laying adult worms (normally an IS t oday process). Knowledge of timing of tlprocess is important since arrested larvae aresistant to most anthelmintics .

Southeastern US: in the deep South, thinare a bit more complicated . Extremely Itsummers destroy infective larvae of most woespecies (Haernonchus is a notable exceptionso parasitism is primarily a winter/spri nproblem. This is exacerbated further iunderfed cattle by nutritional stress that mu!be endured each winter (causes loss of acquire simmunity to worms). In general, eggs shed i tfall and winter develop into infective larvae i tlate winter/early spring . Infection and clinicasigns appear shortly thereafter . Arrested devel-opment of larvae occurs during late spring an dsummer. In the fall arrested larvae resum edevelopment and commence laying eggs.Although Haemonclrus placei is often a part ofwinter/spring gastroenteritis in southeasterncattle, outbreaks also have occurred i nreplacement heifers grazing highly improve dsummer pastures at a high stocking rate .

Western US: in the west, worm transmissionis influenced as much by moisture as b ytemperature. Very little worm infection occursin dry western rangeland where cattle do no tgraze irrigated pastures or moist river bottoms .Worm transmission is further confounded byeffects of altitude. At risk of oversimplification, one may assume that wherepastures in the West are reasonably moist,whether by rainfall or irrigation, seasona lpatterns of worm transmission follow that o fthe southeastern US in areas having warmwinters and that of the northern US in areaswhere winters are cold.

Occasionally disease is seen at atypica l

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s of the year. A condition known as Typestertagiosis occurs when massive numbersrrested larvae of Ostertagia simultaneouslyme their development. (In contrast, Type Irtagiosis occurs when newly ingested larvaelop straight to adult worms in largebers, the usual situation in lateer/early spring in the deep South) .

,tment of PG E

animals showing typical signs of type Itse should be dewormed and, if at allble, moved to a worm-free pasture . Failurenove animals may result in promptection and a return of clinical signs. Under

conditions retreatment at 3 or 5nectin) wk intervals may be needed. Whenagain become available for cattle, a

fined release bolus would be helpful in this:ion. For type H disease the treatment o fe is ivermectin. A move to safe pasturely is not needed.

ntion of PGE

lult Cows. Although routine deworming o fing dairy cattle at calving has bee n)ted widely by pharmaceutical companies,come of the properly controlled studie shown a significant response to treatment .fie has identified the factors that causetent of adult cows to be beneficial on onebut not on another. Until more is knownrobably prudent to deworm adult cow swhere a deworming trial has showncial results on that dairy. Such a trial canfie on dairies having good records, e.g.,rould be grouped into 100 or more pairs

similar lactation number and prio rtivity. One cow in each pair would b ened at drying off and freshening and on eentreated and milk production i sred. Worming would be justified if there.e than a 50 lb difference in milktion in favor of treated cows.

lacement Heifers . In contrast to adult

cows, dairy replacement heifers in their firs tseason at grass are highly susceptible toparasitism, and prophylactic treatment yieldsbig returns. In northern states heifers are besttreated at 3 and 6 wk after turn-out to sprin gpasture (3 and 8 wk if ivermectin is used), or asustained release bolus is given. This preventsshedding of eggs onto spring and early summe rpasture that develop into the big July rise ininfective larvae on pasture . An alternativecommonly used in Europe is to treat cattle inJuly and move them to a safe pasture (usuallyone used for spring haying) . No comparabl eprograms have been worked out for the deepsouth. In general, replacement heifers in th esoutheast should be dewormed aggressivel y(repeated treatments or sustained releas eboluses) during the early part of their firstseason on grass .

Lungworm s

Lungworms occasionally cause trouble i ncattle, but disease is much less common no wsince introduction of highly effectiveanthelmintics during the 1970s . Like O. ostertagilungworm appears to be a cool season parasit ein the deep south and a warm season parasit ein northern states . Since there is a rapidlyacquired immunity to this parasite generallyonly young animals are affected. Calves givenearly, low-level exposure to lungwormsnormally acquire strong immunity and neve rdevelop lungworm disease . However, if calvesare exposed to large numbers of infectiv elarvae on pasture or if the level of pasturecontamination increases from a previous lo wlevel so rapidly that acquired immunity canno tkeep pace, lungworm disease will occur. Atypical history is that of young cattle grazingpasture grazed earlier by young animals, ascommonly occurs with dairy replacementrearing. The first group contaminated th epastures with larvae, but acquired immunitybefore disease appeared . The second groupreceived a massive exposure before immunit ycould be acquired. Alternatively, mixingrecently weaned calves from several sources

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double dose (10 mg/kg) of fenbendazole or th elabelled dose of albendazole (also 10 mg/kg) .Treatment of cows usually is not necessary.

Bovine Coccidiosi s

Dairy calves frequently suffer coccidiosis.Bovine coccidiosis is characterized by bloodydiarrhea with resultant anemia, dehydration ,loss of appetite and weight loss . Straining todefecate and coughing from concurrent pneu-monia may result in rectal prolapse . Maggotinfestations may occur secondarily to manur esoiling of the tail and hindquarters. Death mayoccur in severe cases either directly or fro mpneumonia or bacterial infection of theintestine (enteritis) that often accompanies thi scondition. Nervous Coccidiosis is a lesscommon sequel characterized by muscletremors, seizures, blindness, and, commonly,death. Calves and yearlings most commonly areaffected whereas mature cattle generally hav estrong acquired immunity.

Treatment of acute coccidiosis is by hig hdoses of amprolium (10 mg/kg/day X 5 days )or, generally more rewarding, sulfaquinoxaline,plus good nursing care with emphasis o ncontrol of dehydration and secondary bacterialenteritis or pneumonia . Prevention is by goodsanitation, minimizing stress on calves, wit hpreventive medication given only as a las tresort. Lower doses of amprolium ( 5mg/kg/day X 21 days) have encountere dresistance problems. Decoquinate is widelyused in beef feedlots (0.5 mg/kg/day X 2 8days) . The ionophors, monensin and lasalocid ,fed to promote feed efficiency have a mil dcoccidiostatic effect. Strong, healthy calvesreceiving these ionophors may need noadditional coccidiostat . However, severelystressed calves should be given a stronge rcoccidiostat such as decoquinate .

Cryptosporidiosis is associated with neonatalcalf diarrheas, especially in hutch-reared dair yreplacement heifers. There are no specificdrugs for treatment or prevention. Treatment isnon-specific ; maintain hydration, minimize

stress, and administer enteric sulfas to preventsecondary bacterial enteritis until acquiredimmunity ends the disease . Good sanitationand minimizing stresses on neonatal calves i sthe best prevention.

References

Bradley, R.E. 1986 . Efficacy of a morantel sustainedrelease bolus for the control of gastrointestina lnematodes In Florida dairy heifers . Amer. J . Vet . Res.47:2385 .

Dubai, J .P. and Fayer, R. 1986 . Sarcocystosis ,toxoplasmosis and cryptosporidiosis in cattle . VeterinaryClinics of North America (Food Animal) 2:293 .

Ernst, J .Y. and G.W Benz. 1985 . Intestinal coccidiosisin Cattle . Veterinary Clinics of North America (Foo dAnimal) 2:283 .

Herd, R.P. 1980 . Control of internal parasites in dairyreplacement heifers by two treatments in the spring .Journal of the American Veterinary Medical Associatio n177:51 .

Herd, R.P. 1982. Treatment of dairy cattle withsubdinical Intestinal parasitic infections . In D .F. Mettric kand S.S. Desser (eds.) Parasites - Their World an dOurs, Elsevier Biomedical Press, New York, pp. 451 .

Herd, R.P. 1983 . A practical Approach to ParasiteControl in Dairy Cows and Heifers. The Compendiumon Continuing Education 5:s73 .

Kennedy T.J. 1982 . Treatment of subdinical parasitismin dairy cattle . In D.F. Mettrick and S .S. Desser (eds. )Parasites - Their World and Ours, Elsevier Biomedica lPress, New fork, pp . 459.

Malone, J .B. 1986. Fascioliasis and cestodlasis in cattle .Veterinary Clinics of North America (Food Animal )2:261 .

Shearer, J.K, C.H. Courtney, J .S. Brenneman, S .LSumner, and M .C. Speibring . 1984. Liver flukes - Acostly concern. Southeastern Dairy Review 23:12.

Williams, J .C . and J .W Knox. 1988 . Epidemiology ofOstertagfa ostertagl in warm temperate regions of theunited States. Veterinary Parasitology 27:23.

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