Section 10 Bovine Parasitic Diseases
- Rebecca Froehlich
- Research Officer, Sligo Regional Veterinary Laboratory, Doonally, Sligo, Ireland
Parasitic disease is consistently one of the most frequent post-mortem diagnosis in Regional Veterinary Laboratories. In addition, faecal samples are submitted for clinical diagnosis; the majority of these samples come from herds or flocks with animals showing clinical signs of diarrhoea and/or weight loss. Fasciola hepatica (Fasciolosis),Trichostrongylidae (Parasitic Gastro-Enteritis) and Dictocaulus viviparus (Parasitic Pneumonia) are the most important organisms responsible for parasitic disease in cattle and sheep.
Faecal samples submitted to DAFM laboratories are routinely examined for eggs (Trichostrongylidae,1 Fasciola hepatica and C. daubneyi), lungworm larvae (Dictyocaulus viviparus), and coccidial oocysts (Figure 10.1).
10.1 Trichostrongylidae
Ostertagia ostertagi and Cooperia oncophora are the most prevalent nematodes affecting cattle in the Republic of Ireland (Murphy et al. 2006). These parasites can cause parasitic gastro-enteritis with acute clinical disease significantly reducing productivity of affected animals. O. ostertagi triggers two different syndromes in weanlings: Ostertagiosis Type 1 which typically occurs in late summer or autumn after a mass emergence of larvae on fields.
| Cooperia oncophora | Ostertagia ostertagi |
|---|---|
| Small intestine | Glands of abomasum |
| Adult stage 15-18 days PI* | Adult stage 18-21 days PI |
| Immunity develops after first grazing season | Immunity develops after second grazing season |
| * Post-Infection |
Figure 10.1: Modified McMaster fecal egg counting. Microscopic appearance of parasitic eggs and oocysts in a faecal smear: Trichostrongyles (blue arrow), Nematodirus (red arrow), Larvated strongyloid egg (yellow arrow) and coccidial oocysts (green arrow). Photo: Cosme Sánchez-Miguel.
Ostertagiosis Type 2, observed especially in late winter and early spring and caused by larvae which experienced a delayed development in abomasal mucosa (hypobiosis). Ostertagiosis Type 2 usually shows poor response to treatment; however, it can be prevented by appropriate treatment at time of housing. In general, cattle develop immunity to parasites (Table 10.1); this immunity does not prevent infection but halts development of clinical disease.
| Result | No. of samples | Percentage |
|---|---|---|
| Negative | 3625 | 80.0 |
| Low (50-500 epg) | 683 | 15.1 |
| Medium (500-1200 epg) | 132 | 2.9 |
| High (>1200 epg) | 90 | 2.0 |
In the last decade, it has been shown that cows can develop a subclinical parasitic infection with O. ostertagi which can lead to significant production losses linked to reduced milk yields, weight loss, non-specific immune suppression and mortality (Delafosse 2013).
Figure 10.2: Stacked count of bovine faecal samples (all ages) tested per month for Trichostrongylidae during 2018. The percentage in each bar represents positive samples (n= 4530 ).
Faecal samples for investigation of parasitic burden in cattle were received throughout the year with peaks from May to August and in November (Figures 10.2 and 10.3). The peak during summer months covers the traditional grazing season and is most likely due to monitoring efforts. The high number of submissions in November coincides with the beginning of housing, which commonly associates with antiparasitical treatment. The highest amount of samples yielding positive results occurred in spring, late autumn and early winter (Figures 10.2 and 10.3).
Figure 10.3: Percentage of positive bovine faecal samples for Trichostrongylidae eggs in 2018 (n= 4530 ).
10.1.1 Nematodirus spp.
Also called thread necked worms are a species of nematodes which mainly affect small ruminants, but have been reported to cause disease in cattle.
| Result | No. of samples | Percentage |
|---|---|---|
| Negative | 4441 | 98.1 |
| Low (50-500 epg) | 77 | 1.7 |
| Medium (500-1200 epg) | 8 | 0.2 |
| High (>1200 epg) | 3 | 0.1 |
Nematodirus battus is the most significant species in Ireland and affects mainly naive young lambs. N. helvetianus, which is more likely to infect cattle, has been noted across Europe but appears to be more common across Australia and Asia (McMahon et al. 2017).
In 2018, there was an an insignificant number of bovine faecal samples were Nematodirus eggs were present (Table 10.3).
10.2 Coccidia
Coccidia (Eimeria spp.) are protozoa (Figure 10.4 which can cause significant clinical disease in calves and lambs from 3 weeks to 9 months of age. Diarrhoea and dysentery are common signs of clinical coccidiosis. While there is a wide range of coccida species, only three species are considered pathogenic in cattle: Eimeria bovis, Eimeria zuerni and Eimeria alabamensis. Coccidia are host specific.
| Eimeria | Pre-patent period* |
|---|---|
| Eimeria bovis | 21 days |
| Eimeria zuerni | 21 days |
| Eimeria alabamensis | 8-12 days |
| Note: | |
| * Time between infection of the animal and | |
| the first appearance of oocysts in faeces |
- Coccidia have a life cycle of 21 days. Examining calf faeces for oocysts before 21 days of age will produce a false negative result.
- Oocyst production in clinical cases of coccidiosis may be low. Therefore, it is a good idea to sample comrades which are as yet unaffected.
Clinical disease in adults is rather uncommon as immunity to the disease can develop quickly. Disease is usually self-limiting lasting 3–4 weeks, the time frame for parasites to complete their life cycle in host. Infection occurs after ingestion of sporulated oocysts, these release sporozoites that penetrate the epithelial cells of small and large intestine. Further development continues within epithelial cells where coccidia mature and produce oocysts for excretion in faeces; affected epithelial cells are destroyed leading to rapid and severe damage of intestinal epithelium.
| Result | No. of samples | Percentage |
|---|---|---|
| Not Detected | 3536 | 78 |
| Light Infection | 712 | 16 |
| Moderate Infection | 148 | 3 |
| Heavy Infection | 71 | 2 |
| Severe Infection | 39 | 1 |
Figure 10.4: Microscopic appearance of coccidial oocyst in a faecal smear (light microscope at 100x-Oil). Photo: Cosme Sánchez-Miguel.
As in previous years, in 2018 the majority of positive samples contained low numbers of oocysts and would not be considered of clinical significance (Table 10.5).
Figure 10.5: Stacked number of bovine faecal samples (all ages) tested for coccidial oocysts in 2018. The percentage in each bar represents the number of positives (n= 4506 ).
Figure 10.6: Count of bovine faecal samples exmined for coccidial oocysts in 2018 (n= 4506 ).
- Avoidance of faecal contamination of feed and water, maintenance of dry bedding, not mixing age groups and, if necessary, the use of prophylacric anticoccidian drugs help to protect calves from exposure to large amounts of coccidial oocysts. This enables calves to acquired immunity without development of clinical signs and loss in production.
10.2.1 Treatment and control
Anti-protozoal treatment at the occurrence of clinical signs is usually unrewarding as diarrrhoea indicates the end of coccidia life cycle in host and that severe intestinal damage is already present.
Consequently, where high environmental contamination is present, control is best achieved by hygiene and prophylactic treatment.
Currently, there a three anticoccidials registered for the use in bovine in the Republic of Ireland:
- Decoquinate: 60.6 g/kg premix for medicated feeding stuff
- Diclazuril: 2.5 mg/ml oral suspension
- Toltrazuril: 50 mg/ml oral suspension
For further information please refer to the manufacturers’ advice.
10.3 Rumen and Liver Fluke
The most relevant trematodes in Ireland are liver fluke species Fasciola hepatica and rumen fluke species Calicophoron daubneyi. If measured by the detection of eggs in faecal samples, in recent years the prevalence of Fasciola hepatica appears to have declined, whereas rumen fluke appears to stay static ( All-island Disease Surveillance Report,, (Department of Agriculture, Food and the Marine 2018)).
| Result | No. of samples | Percentage |
|---|---|---|
| Liver fluke eggs not detected | 3722 | 97 |
| Positive liver fluke eggs | 131 | 3 |
Figure 10.7: Stacked number of bovine faecal samples (all ages) tested for liver fluke in 2018. The percentage in each bar represents the number of positive samples per month (n= 3853 ).
Fasciola hepatica causes disease in cattle mainly during the chronic phase of the infestation, when adults trematodes inhabit liver tissue. Clinical signs include weight loss, diarrhoea and hypoproteinaemia due to liver damage and epithelial loss in the intestine.
Risk of infection with both parasites varies from year to year depending on climatic conditions, especially rainfall and surface moisture. Wet ground conditions at moderate temperatures, as occurring in Ireland during spring and summer, particularly favour reproduction and spread of the mollusk intermediary host (Galba trunculata), development of fluke in intermediary host and shedding of the metacercaria on pasture.
Every autumn, to assist farmers and private veterinary practitioners, DAFM issues a fluke forecast based on analysis of meteorological data for the preceding 6 months.
In 2018, as in previous years, rumen fluke eggs were more often detected in bovine faecal samples than liver fluke eggs.
Figure 10.8: Microphotography of a Rumen fluke (Calicophoron daubneyi) attached to the rumen wall by its oral sucker. Photo:Cosme Sánchez-Miguel.
| Result | No. of samples | Percentage |
|---|---|---|
| Rumen fluke eggs not detected | 2453 | 64 |
| Positive rumen fluke eggs | 1400 | 36 |
Figure 10.9: Stacked count of bovine faecal samples (all ages) tested for rumen fluke. The percentage in each bar represents positive samples (n= 3853 ).
Rumen fluke is mainly described to cause disease during the juvenile phase of the parasite, when it inhabits the duodenum from several weeks to months, attaching to duodenal wall. Severe disease outbreaks have been described when young animals were exposed to large number of metacercariae in the field (O’Shaughnessy et al. 2018). However, cases of clinical disease are very rare with only 3–4 cases being reported annually in Ireland (Toolan et al. 2015).
To date, adult rumen fluke living in the rumen and attaching to ruminal mucosa are not thought to cause significant disease, however there is some evidence of inflammatory changes occurring in reticulum and rumen during infestation.
Both, liver and rumen fluke parasites, use the same molluscan intermediary host, the mud snail (Galba trunculata), possibly leading to an interspecific competition between larval stages of the two species, which might have an additional impact on the relative abundance of infection. Further research might be needed to elucidate this further (Deplazes et al. 2016).
10.3.1 Treatment and Control
There is a variety of flukicides available for treatment and control of Fasciola hepatica. However, due to regulatory changes in recent years, restrictions apply for use in dairy cattle depending on the active ingredient and the reproductive stage of the animals. Further on, when choosing a suitable treatment, consideration of the developmental stage of the parasite is needed as only some products affect juvenile stages (e.g. Triclabendazole, Closantel, Nitroxinyl) whereas other products only affect the adult stage (>12 weeks) of the parasite. Depending on the product and the time of application (e.g. at housing) a repeat or delay in treatment might be appropriate.
Sedimentation method detects both eggs, Fasciola hepatica (liver fluke) and Calicophoron daubneyi (rumen fluke).
The significance of rumen fluke eggs in cattle faeces is difficult to determine, adults are not considered to be pathogenic while larvae are. If eggs are found in a number of animals with poor thriving, treatment may be warranted. Alternatively, if eggs are found in healthy cattle in good condition, it may be wise just to monitor thrive.
Finally, there is also evidence that there is emerging resistance against some flukicides , in particular Triclabendazole, consequently, the choice of appropriate flukicide, needs to be prudent and circumspect (Kelley et al. 2016). A comprehensive list of available flukicides, including restrictions, is available from the Irish Health Products Regulatory Authority (HPRA). To date, there is no registered treatment for rumen fluke (C. daubneyi) available. However, there has been evidence that some products like oxyclozanide and closantel show good activity against adult rumen fluke infestation and lead to a reduction in faecal egg count. Dose rates and related side effects, as well as route of administration, appear to have an impact on treatment success (Arias et al. 2013, Malrait et al. (2015)).
References
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Delafosse, Arnaud. 2013. “The Association Between Ostertagia Ostertagi Antibodies in Bulk Tank Milk Samples and Parameters Linked to Cattle Reproduction and Mortality.” Veterinary Parasitology 197 (1): 212–20. doi:https://doi.org/10.1016/j.vetpar.2013.05.023.
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Department of Agriculture, Food and the Marine. 2018. “Policy on Highest Priority Critically Important Antimicrobials.” Dept. of Agriculture, Food; the Marine. https://www.agriculture.gov.ie/media/migration/animalhealthwelfare/amr/PolicyHighestPriorityCriticallyImpAntimicrobials191118.pdf.
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Toolan, Dónal P., Gillian Mitchell, Kate Searle, Maresa Sheehan, Philip J. Skuce, and Ruth N. Zadoks. 2015. “Bovine and Ovine Rumen Fluke in Ireland—Prevalence, Risk Factors and Species Identity Based on Passive Veterinary Surveillance and Abattoir Findings.” Veterinary Parasitology 212 (3): 168–74. doi:https://doi.org/10.1016/j.vetpar.2015.07.040.
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Kelley, Jane M, Timothy P Elliott, Travis Beddoe, Glenn Anderson, Philip Skuce, and Terry W Spithill. 2016. “Current Threat of Triclabendazole Resistance in Fasciola Hepatica.” Trends in Parasitology 32 (6). Elsevier: 458–69.
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Malrait, Karen, Sien Verschave, Philip Skuce, Hans Van Loo, Jozef Vercruysse, and Johannes Charlier. 2015. “Novel Insights into the Pathogenic Importance, Diagnosis and Treatment of the Rumen Fluke (Calicophoron Daubneyi) in Cattle.” Veterinary Parasitology 207 (1): 134–39. doi:https://doi.org/10.1016/j.vetpar.2014.10.033.
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