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Control of Fluke (Fluke in the animal (Rumen fluke (Excysts in the…
Control of Fluke
Fluke in the animal
Rumen fluke
Excysts in the duodenum, feeds on mucosal wall and causes significant damage, migrates up the GI tracts to the rumen where it attaches to the rumen wall and feeds on rumen fluid- not pathogenic at this stage
Liver fluke
Excysts in duodenum and burrows through intestine walls to liver, migrates through liver causing significant liver damage, eventually reaches the bile ducts at 6-8 weeks where it feeds on blood and lays its eggs.
Disease = Fasciolosis can be acute due to large number of migrating fluke, subacute- combination of immature and adult and chronic - adult fluke feeding on blood.
Effects of fluke
Liver fluke
Mazeri et al., 2017 - modelling suggests that beef cattle infected with live fluke take longer to fatten >10 flukes = 77 extra days
Bovine tb skin test and blood test are less sensitive in liver fluke infected cattle, this is due to fluke suppressing the immune system resulting in a smaller reaction to the bTB tests. The same immune supression may increase susceptibility to salmonella and clostridium infections.
How ell et al., 2015 - exposure to liver fluke associated with lower milk yields
Sheep are less tolerant of fluke infection - historic problem known as black disease - clostridium novyi usually in gut but some can lodge in the liver where they remain dormant until damage occurs creating anaerobic conditions in which they can germinate causing necrosis and widespread damage - results in subcutaneous bleeding and blackening of the skin.
Rumen fluke
Can cause disease and mortality but official cases remain rare as massive juvenile stage infection is required
Increasing in prevalence - 51% of welsh farmers had not heard of rumen fluke - yet it was present on 61% of farms studied had cases.
Fluke and climate change
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Ollenshaw index used to predict liver fluke risk across the UL, work has shown that the same index has an association with rumen fluke distribution in welsh herds - Fox et al., 2011- predicted a huge increase in the severity of fluke outbreaks by 2070 with some areas of wales having serious epidemics and cases occurring in winter as well as summer
Fluke Anthelmintics
Different anthelmintic classes can treat fluke but only tricalbendazole has efficacy against immature fluke - resistance is widespread. Oxyclozanide is the only compound with efficacy against rumen fluke.
control of fluke
Focus on reducing anthelmintic usage to slow resistance development- complex parasite with varying stages of infection. Also has clear risk areas and risk periods
Fluke TST - not really an option at present, animals are not capable of developing adaptive immunity- fluke infections are not uniform due to behaviour (animals grazing in different areas)
Refugia not applicable as farmers cannot leave liver fluke untreated as even low infection levels results in a significant production loss + a welfare issue.
Fluke TT - FEC - can be used by big problem= only adult fluke lay eggs and it is the juvenile flukes that cause the problem
FEC = best of a bad bunch and only test for RF - ELISA can test for LF but only as a measure of exposure not present infection. abattoir feedback can be informative but is reactive not proactive
TT - Timed housing - housing allows the opportunity to remove all fluke from livestock, can treat all cattle 6-8 weeks post housing with an adult killing anthelmintic however major issues with withdrawal period in dairy cattle - spring/early summer not associated with fluke disease cattle released in spring will not shed eggs if correctly treated while housed.
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