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Articles 2020-24 > Parasito > Flashcards

Parasito Flashcards

1
Q

Are methods of non-drug control effective in reducing the parasite burden on pastures ?

A

Removal of feces twice weekly → effective means of reducing fecal egg shedding and thus reduces the need for anthelminthics.
Phytotherapies cannot be recommended currently.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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2
Q

Does targeted selective treatment (TST) slow the spread of anthelmintic resistance in cyathostomins ? (4 points)

A
  • ≦ 2 treatments per horse per year could slow the dev of resistance.
  • Use of targeted selective TT (TST) is strongly indicated in spring.
  • Higher TT thresholds around 500-600 epg shloud be considered.
  • During autumn / winter, it may be less deleterious to treat the whole herd.
  • Resistance develops more rapidly in younger animals, therefore TST should not be restricted to older animals.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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3
Q

What is the minimum requirement for strongyles fecal egg counts (FEC) ? (4 points)

A
  • ∼ 20% of the herd shedding > 80% of the total eggs shed.
  • Each fecal sample should be collected from multiple sites across a pile of feces, stored at < 6°C under anaerobic c°.
  • Choice of FEC is dependent on its application : high egg shedding horses → McMaster ; FECRT (lower egg count) → higher accurate method (Mini-FLOTAC or FECPAK)
  • Higher threesholds ∼ 500-600 epg should be considered.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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4
Q

Should combined anthelmintic use be considered for the TT of nematodes ?

A

Combination TT may be indicated in cases of anthelmintic resistance to improve TT efficacy. But improved efficacy may be short lived and there are concerns over the long-term effects.
This approach cannot be recommended until there is further research to demonstrate that the benefits outweight the risks of increasing overall exposure to anthelmintics.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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5
Q

In young horses, how important is the clinical problem related to Parascaris spp. infection ?

A
  • Infection with Parasacaris is common in young horses (∼38%)
  • Subclinical disease is poorly described, and clinical disease is uncommon and unpredictable.
  • Infestation must be taken seriously as morbidity and mortality associated with luminal obstruction are high.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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6
Q

In young horses, what are the available diagnostic methods for Parascaris infection ? How reliable are they ?

A
  • Diagnosis of Parascaris infection is largely reliant on egg detection in feces, using conventional FEC methods.
  • Optimal FEC method → unknown
  • Parascaris FEC → unlikely to reflect parasite burden and should not be used to predict risk of parasite-related disease.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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7
Q

What are the patterns of anthelmintic resistance in the Parascaris population?

A
  • Woldwide → extensive evidence of macrocyclic lactone resistance in Parascaris populations, likely as a result of extensive use in foals and increased selection pressure with ML use through larvicidal efficacy and removal of an important source of refugia.
  • Increasing evidence of Parascaris resistance to BZ and pyrantel → need for determining anthelmintic efficacy/resistance through FEC reduction tests on all individual farms.
  • Larvicidal activity of fenbendazole (5 daily treatments) → increasing fenbendazole resistance

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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8
Q

What is parasite refugia ? How is it related to anthelmintic resistance ?

A

Refugia refer to the portion of a population of parasites (all free-living parasite stages on the pasture, all parasites from untreated animals) or stages of parasites (larval stages) that is not affected by the treatment.
The higher the proportion of worms in refugia, the more slowly resistance develops. The worms in refugia are not under selection pressure for resistance, thus resistant worms remain diluted by susceptible worms.

AAEP Internal Parasite Control Guidelines

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9
Q

In young horses, what are the clinical consequences of anthelmintic resitance of Parascaris ?

A

Increasing Parascaris-associated disease → increasing resistance ?
Faecal egg count reduction tests should be performed for all classes of anthelmintics to establish local resistance patterns.
There are concerns that the increased frequency with which fenbendazole and pyrantel are now being used will accelerate development of resistance to these anthelmintics.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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10
Q

What are the management strategies to reduce the Parascaris burden and delay the development of anthelmintic resistance ?

A
  • Management strategies to reduce environmental contamination → manure and bedding collection at least twice weekly and appropriate composting of feces before spreading in pasture (parascaris eggs are rendered non-viable by composting).
  • Delaying the development of anthelmintic resistance is primarily reliant on reduced anthelminthic use and preservation of refugia of susceptible genotypes.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024
ESCCAP guidelines 2019

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11
Q

Does anthelmintic administration increase the risk of Parascaris-associated disease ?

A

Foals that develop Parascaris impaction of the SI commonly have a history of recent anthelmintic adm°, usually within the preceding 24h.
If heavy burdens and high risk of colic → do not use immediate killing/paralysis drugs (ML, pyrantel, piperazine). Prefer benzimidazoles (inhibition of microtubule formation, slow mechanisme of action) .

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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12
Q

Is the national / international horse movement associated with increased risk of dissemination of anthelmintic-resistant Parascaris ?

A

There are no studies of the implications of horse movement on the dissemination of anthelmintic-resistant Parascaris. However, horse movement has been associated with dissemination of resistant cyathostomins and likely represents a risk for transmission of resistant Parascaris.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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13
Q

How to do a FECRT (Fecal Egg Count Reduction Test) ? For what purpose ?

A

The Fecal Egg Count Reduction Test (FECRT) is the only method currently available for detecting resistance in parasites of horses.
To perform the FECRT, a fecal sample is collected prior to
deworming. The anthelmintic is administered and a fecal sample is collected 10-14 days following treatment.
FECRT should be performed in groups (≧5 horses) rather than individuals.
The mean reduction for all horses tested is calculated to determine the % reduction for the farm or stable.

AAEP Internal Parasite Control Guidelines

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14
Q

How can FECRT be used to determine resistance?

A

Target efficacy for each drug class is different.
* ivermectin / moxidectin → expected efficacy = 99.9%
* benzimidazoles = 99%
* pyrantel = 98%

A lower target efficacy of 92% is recommended for determining resistance in a clinical setting, results in the range 92%- 99.9% for ivermectin and moxidectin are inconclusive.
Repeat FECRT at 6 weeks for ML resistance (Egg Reappearance Periode - ERP)

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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15
Q

Which anthelmintic drugs can be used to control cyathostomin populations in the UK ?

A

Cyathostomin resistance to :
* BZ is very common (possibly ubiquitous),
* pyrantel common,
* ivermectin/moxidectin emerging.
The resistance is probably more likely in young stock. Where they remain effective, it is important to use BZ and PYR to reduce the selection pressure on ivermectin and moxidectin.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

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16
Q

What are the efficacy of anthelmintic drugs against adult/larval stages of cyathostomins (in the absence of resistance) ?

A
  • Adult cyathostomins : BZ, pyrantel, ivermectin, moxidectine
  • Luminal larvae : BZ, ivermectine, moxidectine
  • Encysted larvae : BZ, moxidectine

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

17
Q

What is the Egg Reappearance Period (ERP) ?

A

The ERP is defined as the time interval between the last effective anthelmintic treatment and the resumption of strongyle egg shedding.
This is measured by performing weekly FECRTs until
egg reappearance is seen (< 80% for benzimidazoles and pyrantel, and < 90% efficacy for ivermectin and moxidectin).
The ERP is irrelevant if drug resistance is already present, as there is no egg disappearance.

AAEP Internal Parasite Control Guidelines

18
Q

Which horses are at risk of developing cyathostominosis?

A
  • Younger horses (< 6 years old) are at significantly higher risk of larval cyathostominosis.
  • Horses >18 years old might represent a separate high-risk group with a less seasonal presentation.
  • More frequently during winter and spring, between November and March.
  • Anthelmintic administration may precipitate disease.

While larvicidal treatment in early winter has traditionally been recommended in high-risk populations to prevent the disease, there is no evidence that this practice reduces risk.
Low risk populations which are well managed should not require routine larvicidal treatment.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024
Larval cyathostominosis: Clinicopathological data and treatment outcomes of 38 hospitalised horses (2009–2020)
eve 2023

19
Q

Can ELISA be used to identify horses in need of anthelmintics to prevent larval cyathostominosis ?

A

As the test is unable to differentiate infection with larval versus adult cyathostomins, it cannot be used to confirm larval cyathostominosis as a cause of disease although a negative result may allow cyathostominosis to be eliminated as a differential diagnosis.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

20
Q

What diagnostic tests should be used for tapeworm infection (Anoplocephala perfoliata)?

A

Not all horses with evidence of exposure require treatment. Prevalence ∼ 51 - 69%
Assessment of antibody levels (serological and salivary Ab test) and/or FEC can be used to identify horses with clinically relevant tapeworm burdens.
Testing on a herd basis to compensate for the limited Se → all animals treated if positive

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

21
Q

Which horses are at risk of tapeworm infection ?

A
  • Horses of all ages can be infected at any time of the year (mostly end summer) however young horses (1-5 years) are over-represented.
  • Risk of infection rises with increased access to grazing.
  • Need for treatment in any individual or population should be determined by performing group basis diagnostic testing (suggested FEC ≧ 20 parasites).

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

22
Q

How to treat tapeworm infections ?

A

Praziquantel and pyrantel (double dose)
A single annual TT in late autumn or winter
While lack of efficacy has been reported, it is unclear whether this represents resistance due to insensitive FEC and FECRT.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

23
Q

Is treatment of liver fluke required in horses that are being co-grazed with ruminants ?

A

A history of co-grazing with ruminants is common in horses testing positive for fluke infection. Disease due to Fasciola hepatica does not appear to be prevalent in UK.
Co-grazing with ruminants does not necessitate routine prophylaxis for liver fluke infection, routine use will likely lead to flukicide resistance and therapeutic failure.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

24
Q

Should we be concerned that Strongylus vulgaris infection will increase with the restriction of anthelmintics ?

A

S. vulgaris is a possible cause of fatal non-strangulating intestinal infarction. The risk of exposure will increase with reduced anthelmintic adm°.
However, S. vulgaris is likely to remain an uncommon cause of colic and the adm° of ML every 6-12 months in higher risk horses should be adequate.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

25
Q

How to manage horses with signs of Oxyuris equi (pinworm) infection ?

A
  • ML and fenbendazole → effective against O. equi, but ML resistance is increasing.
  • Pyrantel → variable efficacy
  • Animals showing significant perineal pruritus where O. equi eggs are identified on tape strip examination should be treated with benzimidazoles alongside cleaning of the perineum at least every 3 days to limit environmental contamination.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

26
Q

Should lungworm be considered in deworming programmes in the UK ?

A

Lungworm does not need be considered in horses that are not grazing with donkeys. Where donkeys are present, the true risk to horses is unknown but is likely to be low given the paucity of reports.
Dictyocaulus arnfieldi is thought to be sensitive to most anthelmintics such that specific treatment for this parasite is unlikely to be necessary.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

27
Q

Should we consider Onchocerca cervicalis as a cause of skin lesions ?

A

Adult Onchocerca cervicalis reside in the nuchal ligament.
Larval migration can be associated with alopecia and pruritus around the head, neck, trunk and especially around the umbilicus. Abberant migration → eye and suspensory ligament.
Although disease is rare in the United Kingdom, dermatitis of the predilection sites in warmer months, or in imported horses, should prompt veterinarians to consider O. cervicalis.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

28
Q

What is Thelazia lacrymalis responsible for?

A

In warmer climates, Thelazia lacrymalis is commonly identified in the lacrimal glands and nasolacrimal ducts and occasional results in clinical signs of conjunctivitis, blepharitis and epiphora. It is assumed to be spread by flies which are an intermediate host.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

29
Q

Is treatment of Strongyloides westeri necessary in the mare and/or foal ?

A
  • Strongyloides westeri infection is considered asymptomatic in mares. Spread to foals via environmental and transmammary routes.
  • Strongyloides is usually a self-limiting infection in the young foal that has limited clinical effects.
  • Treatment should be reserved for foals with diarrhea associated with high levels of Strongyloides egg shedding.
  • Ivermectin or fenbendazole (50 mg/kg !)
  • Routine treatment of mares before foaling is inappropriate and likely to contribute to the development of resistance in other parasites.
  • Importance of pasture and stable hygiene

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

30
Q

Do horses require treatment of Gasterophilus (bot flies) ?

A
  • Adult flies lay eggs on the hair of horses that are transmitted to the gastrointestinal tract via self or mutual grooming.
  • L1 larvae are found in the oral cavity and migrate through the mucous membranes of the tongue, gums, and palate, causing gingivitis and pain.
  • Gasterophilus spp L2/L3 larvae are found attached to the mucosa of the stomach, duodenum, or rectum of the horse. There is no evidence that larvae are consistently associated with equine gastric disease.
  • Gasterophilus has very low pathogenicity. Large burdens within the stomach are typically asymptomatic.
  • Specific treatment is unlikely to be of benefit and parasite control programs that involve at least annual adm° of a macrocyclic lactone are expected to prevent acumulation of large burdens.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

31
Q

Is the use of equine anthelmintic associated with a threat to local ecosystems ?

A

Moxidectin and ivermectin have marked long-standing effects on terrestrial and aquatic invertebrates and their use impacts ecosystems and soil quality.
The use of these compounds should be minimised, and measures should be taken to limit environmental contamination for as long as possible after treatment and for at least the period of maximum excretion at 2-3 days.
For example :
* collecting and composting faeces for at least a week after adm° of ML,
* keeping horses stabled after administration,
* avoiding pasture contamination with contaminated faeces when the ground is wet or heavy rainfall is anticipated,
* keeping horses that have recently been treated away from watercourses or standing water.

BEVA primary care clinical guidelines: Equine parasite control
evj 2024

32
Q

How to consider a newly introduced horse to prevent importation of new parasite species +/- resistance ?

A

To prevent importation of new parasite species and/or resistant parasite populations, each horse newly
introduced to a farm should be quarantined and treated upon arrival.
Subsequently, the horse should only be put out to pasture after a faecal examination conducted five days post therapy has confirmed that the horse is not shedding worm eggs and that treatment was successful.

ESCCAP guidelines 2019

33
Q

What is the survival rate of referred cases of larval cyathostominosis ? What are the negative prognostic factors ? (4)

A

Low survival rate of referred cases → 55% mortality
Associated with non-survival :
* history of recumbency,
* isotonic fluid therapy,
* increased SAA and low TP at admission,
* low last recorded TP and alb.

Larval cyathostominosis: Clinicopathological data and treatment outcomes of 38 hospitalised horses (2009–2020)
eve 2023

34
Q

What are the clinical consequences of the reduction in use of anthelmintic drugs vs Ascarids and Strongylids in foals and mares ?

A

Anthelmintic treatment intensity was lowered from the traditional intensive regimes without measurable negative health consequences for mares and foals, even if higher ascarid and strongylid egg count levels on stud farms.

Monitoring equine ascarid and cyathostomin parasites: Evaluating health parameters under different treatment regimens
evj 2021

35
Q

What is the efficacy of moxidectine on Strongyle in Southeast England ?

A

Acceptable efficacy of moxidectin at 14 days after
treatment, using FECRT.
However, the ERP pattern measured across the group suggests that this anthelmintic has a considerably shorter suppressive effect on strongyle egg shedding than measured when it was first introduced (12–16 weeks).

Strongyle egg reappearance periods following moxidectin treatment in horses in Southeast England
eve 2024

36
Q

What is the correlation between the risk of positive S. westeri infection and the day of the year ? The age of the foal ?

A

Later born foals had a higher probability of S. westeri infection, suggesting cumulative environmental contamination.
Negative correlation with age.
It may be prudent to consider environmental management practices before implementing a peripartum ivermectin protocol.

Strongyloides westeri infection on a Thoroughbred breeding farm in Ireland (2014–2019): Prevalence, risk factors and peripartum ivermectin
eve 2023

Articles 2020-24 (8 decks)

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