Speak of the devil: Sal­mo­nella strikes again

Irish Examiner - Farming - - DAIRY SECTOR - Paul Red­mond, MVB, MRCVS, Cert DHH, Dun­ta­hane Vet­eri­nary Clinic, Fer­moy, mem­ber prac­tice of Prime Health Vets

This past week proved to be an event­ful one. Fol­low­ing last week’s article about Sal­mo­nella, we had a client with an out­break of Sal­monel­losis.

It is rather scary when it hap­pens, and all the ques­tions are asked over and over. What causes it, where does it come from, how does it spread, and what can I do now? Sal­mo­nella or­gan­isms (and there are hun­dreds of types) are world­wide. They in­fect and cause dis­ease in hu­mans and ba­si­cally any type of an­i­mal that you can think of.

I find this fright­en­ing. Mice and rats on a farm can be a reser­voir of Sal­mo­nella, and birds like gulls and pi­geons have been im­pli­cated in the spread of the dis­ease.

Across all species, most at risk are those with a com­pro­mised im­mune sys­tem, like the young, the old, the sick, the preg­nant etc. The most com­mon symp­tom is di­ar­rhoea, but if it crosses out of the gut, we can have arthri­tis, menin­gi­tis, dry gan­grene, pneu­mo­nia, or the ma­jor scourge of an abor­tion storm.

Fol­low­ing treat­ment, clin­i­cal signs dis­ap­pear (clin­i­cal cure), but the bac­te­ria are of­ten hid­ing out in the gall­blad­der, lymph nodes or ton­sils, so we don’t have a bac­te­ri­o­log­i­cal cure. Gen­er­ally, calves do not be­come car­ri­ers, but all adult cat­tle be­come car­ri­ers for up to ten weeks, with some adults shed­ding Sal­mo­nella bac­te­ria for years af­ter some form of stress like calv­ing, dry­ing-off, drought, trans­porta­tion, a pe­riod of poor nu­tri­tion, or par­a­site in­fec­tion (par­tic­u­larly fluke). As I said here last week, the most com­mon means of spread is by the faeco-oral route, through the mouth. Sal­mo­nella is passed on through milk, eggs, birth flu­ids, but most typ­i­cally through fae­ces.

Poor hy­giene or dirty con­di­tions in­crease this spread. In­fec­tions with Sal­mo­nella in food-pro­duc­ing an­i­mals present a se­ri­ous pub­lic health con­cern. Be­cause Sal­mo­nella is a zoonotic dis­ease, it can eas­ily spread from your an­i­mals to you or your fam­ily.

If you have had an out­break, you re­alise the im­por­tance of strict hy­giene on the farm. No doubt, you are still vac­ci­nat­ing against Sal­mo­nella. If you have stopped, I urge you to start again. With a vast amount of po­ten­tial reser­voirs of in­fec­tion on all farms, it is im­per­a­tive to give your live­stock pro­tec­tion. The vac­cine pro­duces an­ti­bod­ies in the vac­ci­nated an­i­mal. If this an­i­mal gives birth shortly af­ter, the colostrum will con­tain an­ti­bod­ies to pro­tect the new born calf.

If start­ing a vac­ci­na­tion pro­gramme, be­cause of an out­break, you should iso­late and treat clin­i­cally af­fected an­i­mals, and vac­ci­nate the rest.

The iso­lated an­i­mals should be started on the vac­ci­na­tion pro­gramme when they re­cover. A small num­ber of in­di­vid­u­als may not re­spond to vac­ci­na­tion, due to im­muno­log­i­cal in­com­pe­tence or some other rea­son, like a poor nu­tri­tional sta­tus. The ini­tial course of the vac­cine is two doses un­der the skin, as asep­ti­cally as pos­si­ble, at least 21 days apart. If the cow or heifer has not calved within eight weeks of the sec­ond shot, the man­u­fac­turer rec­om­mends a third shot three to four weeks be­fore calv­ing, to boost an­ti­bod­ies in the colostrum, and to give ex­tra pro­tec­tion around the stress­ful time of calv­ing.

For best pos­si­ble re­sponse, it is rec­om­mended not to give any other vac­cines within 14 days be­fore or af­ter the Sal­mo­nella vac­cine.

It is also rec­om­mended to re-vac­ci­nate all stock prior to any pe­riod of stress, and at least within ev­ery 12 months.

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