Which worms up­set your heifers?

Dairy News Australia - - ANIMAL HEALTH - GEMMA CHUCK • Dr Gemma Chuck is a vet­eri­nary ad­viser at Apiam An­i­mal Health.

AS WE come to the end of win­ter and spring ap­proaches, it is time to think about how the change in sea­son can af­fect the bur­den of in­ter­nal par­a­sites in weaned stock. This ar­ti­cle dis­cusses the com­mon gas­troin­testi­nal worms and how they can af­fect dairy heifers.

The com­mon gas­troinesti­nal worms

Gas­troin­testi­nal worms in cat­tle are di­vided into ne­ma­todes (round worms), ces­todes (tape­worms) and trema­todes (flukes). They are as­signed to one of th­ese groups ac­cord­ing to their struc­ture. Within each group, the life cy­cles and growth of the par­a­sites are gen­er­ally very sim­i­lar and dif­fer­ent from those of the other two groups. The ne­ma­todes are the most eco­nom­i­cally im­por­tant in­ter­nal par­a­site of cat­tle. Tape­worms play a mi­nor role and flukes cause sig­nif­i­cant eco­nomic losses in some ge­o­graphic ar­eas.

The ne­ma­todes (round worms)

The small brown stom­ach worm, Osterta­gia os­tertagi, pen­e­trates the lin­ing of the abo­ma­sum (fourth stom­ach) caus­ing se­vere dam­age and in­flam­ma­tion. In­fected heifers have a se­vere scour, in­ap­pe­tence, anaemia and weight loss. Cat­tle up to 18 months old can be af­fected. This par­a­site can en­ter an ar­rested phase of its life­cy­cle which then can then re­sume 3–9 months later. This type of dis­ease can cause sig­nif­i­cant losses in young heifers as the worm lar­vae emerge. The Bar­bers Pole worm, Hae­monchus pla­cei, thrives in north­ern NSW and QLD where there is sum­mer rain­fall. This blood suck­ing par­a­site also in­hab­its the abo­ma­sum and causes se­vere anaemia and loss of pro­tein. This re­sults in the char­ac­ter­is­tic ‘bot­tle jaw’ ap­pear­ance with af­fected cat­tle be­ing weak and slow to move. The stom­ach hair worm, Tri­chostrongy­lus axei, is the last of the com­mon abo­masal ne­ma­todes. It also dam­ages the lin­ing of the abo­ma­sum caus­ing in­flam­ma­tion and re­duced ab­sorp­tion of nu­tri­ents. The stom­ach hair worm is of­ten di­ag­nosed in mixed worm bur­dens and ex­ac­er­bates the sever­ity of an in­fec­tion. The main species of small in­testi­nal worm af­fect­ing cat­tle is Coope­ria spp. Th­ese worms are of­ten present in mixed in­fes­ta­tions. Af­fected an­i­mals will have di­ar­rhea, poor weight gain and in­ap­pe­tence.

The trema­todes (flukes)

Both the liver fluke (Fas­ci­ola hep­at­ica) and the stom­ach fluke (param­phis­tomes) re­quire a par­tic­u­lar species of aquatic snail in or­der to com­plete their com­plex life cy­cle. For this rea­son cat­tle be­come in­fected in only cer­tain re­gions of Australia where th­ese snails co-habit. Con­tact your lo­cal vet­eri­nar­ian to find out if liver fluke is present in your area. Liver fluke in­fec­tion re­sults in sig­nif­i­cant dam­age to the liver tis­sue and bile ducts which causes ir­re­versible scar­ring. Signs of liver fluke in­clude in­ap­petance, weight loss, ‘bot­tle jaw’, anaemia, jaun­dice and death.

The ces­todes (tape­worms)

Th­ese worms are long and seg­mented, mea­sur­ing up to 6 me­tres in length. They com­monly in­habit the small in­tes­tine but their pres­ence is usu­ally of no con­se­quence, hav­ing lit­tle ill-ef­fect on the an­i­mal. Heavy worm bur­dens may com­pete for nu­tri­ents and interfere with gut motil­ity lead­ing to poor weight gain. The main con­cern with tape­worms in cat­tle is from a hu­man health per­spec­tive.

The im­pact of gas­troin­testi­nal worms in cat­tle

As de­scribed, the clin­i­cal signs of gas­troin­testi­nal worm bur­dens in­clude weight loss, ill-thrift, di­ar­rhoea and de­hy­dra­tion. Re­search has shown that even low-level in­fec­tions can have a neg­a­tive ef­fect on pro­duc­tiv­ity in young an­i­mals, such as dairy re­place­ment heifers. Th­ese heifers may not show overt clin­i­cal signs and thus are de­scribed as hav­ing sub­clin­i­cal in­fes­ta­tions. They may have a sup­pressed ap­petite and re­duced pro­duc­tive graz­ing be­hav­ior, lead­ing to re­duced feed in­take and growth. Worm lar­vae cause a sig­nif­i­cant im­mune re­sponse which can lead to chronic in­flam­ma­tion and gut hy­per­sen­si­tiv­ity. Young, grow­ing heifers are highly sus­cep­ti­ble to gas­troin­testi­nal par­a­sitism and the pro­duc­tion losses in this group of an­i­mals will be the great­est. If there has been sus­tained ex­po­sure to worms, adult cat­tle will gen­er­ally de­velop good im­mu­nity by 18 to 20 months of age. Next month we will dis­cuss the treat­ment and man­age­ment of gas­troin­testi­nal worms in cat­tle.

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