Sustainable Control of Equine Endoparasites

Question 1

What are the main parasites that cause health issues in horses?

Answer 1

Cyathostomins, strongyles, anoplocephala perfoliata (tapeworm), parascaris equorum.

Question 2

1. How long can cyathostomin larvae encyst for?
2. What does mass emergence if cyathostomins cause?
3. What is the PPP of strongyles?
4. How are strongyles mostly eliminated?
5. Where are strongyles on the rise? – why?
6. What do strongyles cause?

Answer 2

1. > 3yrs.
2. Colitis and severe diarrhoea and endotoxemia. Can be life threatening.
3. > 4mths.
4. Serial dosing.
5. Denmark – anthelmintics are POMs.
6. Arteritis which causes vascular compromise and ischaemic bowel, requiring surgical resection.

Question 3

1. In what disease is tapeworm in horses implicated?
2. IH of tapeworm?
3. Appearance of parascaris equorum?
4. Is parascaris equorum an issue in adults? – why?
5. Clinical issue w/ parascaris equorum in foals.

Answer 3

1. Intussusception colic.
2. Oribatid mite.
3. Large thick white worm.
4. Rarely – more of an issue in foals so they develop a good immunity to it.
5. Heavy infections can cause blockages of intestine esp. after treatment where they pass through the intestinal tract and get stuck.
   Also likely to be element of disease associated with migration of these parasites across the liver and the lungs.

Question 4

What can cause liver disease in horses?

Answer 4

Liver fluke.

Question 5

Diagnosis of equine endoparasites.

Answer 5

• Post mortem – gold standard but invasive.
• FECs – Various methods. NOTE: cannot differentiate cyathostomins from large strongyles unless eggs cultured to L3 stages.
• Cyathostomin (redworm) ELISA.
• Tapeworm = tricky – eggs t=not easily detected in FECs – serology tapeworm ELISA, saliva tapeworm ELISA, sedimentation w/ flotation method.

Question 6

1. Sensitivity of FLOTAC.
2. Sensitivity of centrifugal-flotation.
3. Sensitivity of FECPAK.
4. Sensitivity of (Modified) McMaster technique.
5. Ovatec sensitivity.
6. What is the problem with FECs?

Answer 6

1. 1 epg.
2. 1-9 epg.
3. 20 epg.
4. 15-100 epg.
5. Qualitative.
6. Only determines presence of reproducing adult females. And does not necessarily reflect the adult worm burdens – esp. parascaris equorum.
   Notoriously poor for assessing tapeworm.
   Variability in daily shedding level.
   Sampling and storage techniques can affect results.
   Variability in distribution of eggs in the faeces.

Question 7

FECs – when to treat?

Answer 7

Use 200 epg as cut off.
Take particular care in late autumn as lower positive counts may be significant with encysted cyathostomins.
Ascarids are highly prevalent layers and counts do not accurately represent burden, treat when positive. Same for tapeworm.

Question 8

1. What does the Small Redworm blood test indicate?
2. What is the Small Redworm blood test used in conjunction with?

Answer 8

1. Antibody levels to the larvae the horse has been exposed to recently.
2. assessment of risk and FECs.

Question 9

Low risk…
1. Previous FEC results.
2. Environmental conditions.
3. What to do in low risk for cyathostomin infection.

Answer 9

1. Always <50epg.
2. • Closed herd.
     - All herd <200epg.
     - Good paddock management.
     - Effective quarantine.
     - Low stocking density.
     - Frequent poo picking.
3. Test w/ Small Redworm blood test.

Question 10

Moderate risk…
1. Previous FEC results.
2. Environmental conditions.
3. What do youm do in situation of moderate risk of cyathostomin infection?

Answer 10

1. Usually <200epg.
2. • Closed herd.
     - Low proportion of herd >200epg.
     - Good paddock management.
     - Medium stocking density.
     - Sporadic poo picking.
3. Test with Small Redworm blood test.

Question 11

High risk…
1. Previous FEC results.
2. Environmental conditions.
3. What do you do in situations of high risk of cyathostomin infection?

Answer 11

1. Recent results >200epg.
2. • High herd turnover.
     - High proportion of herd >200epg.
     - Poor paddock management.
     - Presence of youngstock.
     - High stocking density.
     - No poo picking.
     - Anthelmintic resistance identified.
3. Treat with moxidectin.

Question 12

What are anthelmintic pharmaceutical options?

Answer 12

Benzimidazoles (Fenbendazole, Mebendazole). e.g. Panacur.
– Reports of resistance.
Tetrahydropyrimidines (Pyrantel). Kills roundworm and tapeworm.
– Reports of resistance.
Acylated quinolone pyrazines (Praziquantel). Kills tapeworm.
Macrocyclic lactones.
(Avermectins – Ivermectin, Milbemycins – Moxidectin). Kills cyathostomins, strongyles and parascaris equorum.
– Issues w/ resistance.

Question 13

1. What anthelmintics are effective against adult cyathostomins?
   – Issue?
2. What anthelmintics are effective against larval cyathostomins in the lumen? – Issue?
3. What anthelmintics effective against encysted EL3 and developing LL3 and L4?
   – Issue?

Answer 13

1. Moxidectin, Ivermectin, Pyrantel, Fenbendazole/Mebendazole.
   – Resistance.
2. Questioned efficacy from Moxidectin and Ivermectin, Fenbendazole/Medendazole effective.
   – Resistance.
3. Questioned efficacy from Moxidectin, Fenbendazole/Mebendazole effective @ 5 day double dose. – Issue.

Question 14

1. What anthelmintic effective against strongylus spp.
2. What anthelmintics effective against oxyuris?
3. What anthelmintics effective against parascaris? – issue.
4. What anthelmintics effective against dictyocaulus?
5. Anoplocephala perfoliata?

Answer 14

1. Moxidectin, Ivermectin, Pyrantel, Fenbendazole/Mebendazole.
2. Moxidectin, Ivermectin (questioned), Pyrantel, Fenbendazole/Mebendazole.
3. Moxidectin, Ivermectin, Pyrantel, Fenbendazole/Mebendazole (questioned).
   – resistance.
4. Ivermectin.
5. Praziquantel, Pyrantel @ 2xdose.

Question 15

1. Why is the effectiveness of Oxyuris questioned?

Answer 15

1. The female resides so close to the anus that exposure to the drug may be considerably low.

Question 16

1. How do you carry out an Faecal Egg Count Reduction Test (FECRT)?
2. What does this test help to establish?

Answer 16

1. FEC on day 0.
   Dose @ 110% estimated bodyweight.
   Then FEC again 14 days after worming.
   Calculate % reduction in FEC.
2. Resistance of the endoparasite to the anthelmintic used:-
   – <90% for fenbendazole.
   –<90% for pyrantel.
   –<95% for ivermectin.

Question 17

Best practices for carrying out FECRT.

Answer 17

• Pick a FECRT w/ low detection limits (high sensitivity).
• Need to test >6 horses in herd to be accurate (ideally all).
• If inconsistent results, consider mis-dosing or underdosing as issue.

Question 18

What anthelmintics are cyathostomins resistant to?

Answer 18

Benzimidazoles – All yards have resistance in UK (2013), single dose considered ineffective.
Pyrantel – in UK, Italy, Sweden, USA.
2/12 yards in UK have resistance (2013).
Can have multiple resistance simultaneously.

Question 19

Immunity against strongyles/cyathostomins.

Answer 19

Slow to develop – 5-6yrs, wanes in older horses.
Less susceptible to severe disease as get older.
Mare still a source of infection for foals.
Adults need to be included in control program.

Question 20

1. What anthelmintics is parascaris equorum resistant to?
2. Immunity against parascaris equorum.
3. Why is parascaris equorum so difficult to get rid of?

Answer 20

1. Macrocyclic lactone resistance reported in ivermectin, moxidectin, benzimidazoles (early).
2. Develop good immunity.
   Readily affects youngstock and foals, seen rarely in adults.
   TAKE CARE W/ IMMUNE SUPPRESSED PATIENTS.
3. Survives for long time on pasture.