Canine and Feline Parasite Control at Home and Abroad

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Canine and feline parasite control at home and abroad

Author : Ian Wright

Categories : Companion animal, Vets

Date : June 13, 2016

ABSTRACT

The European Scientific Counsel Companion Animal Parasites (ESCCAP) UK and Ireland is a national association of ESCCAP Europe, bringing together some of the UK and Ireland’s leading experts in the field of veterinary parasitology.

ESCCAP UK and Ireland works with pet owners and professionals to raise awareness of the threat from parasites and provide relevant information and advice. Part of this service is to answer questions from the public and veterinary professionals asked via www.esccapuk.org.uk

This article addresses the most common questions asked that are of particular relevance to veterinary professionals.

1 / 11 Figure 1. Flea bite reaction.

ESCCAP UK and Ireland is independent, working with pet owners and professionals to raise awareness of the threat from parasites and provide relevant information and advice.

Part of this service is to answer questions from the public and veterinary professionals, asked via www.esccapuk.org.uk

Some questions are specific to individual circumstances, such as trematodes present in Asia and parasites present in the Middle East.

Others, however, are asked frequently and of more general relevance to UK veterinary professionals.

Some examples are discussed in this article and fall into four broad categories:

ectoparasite control in households macrocyclic lactone use European pet travel advice Babesia canis prevention in dogs

Ectoparasite control in households

Questions are often asked about parasites found in the home – either when life stages are discovered in the house or when ectoparasites are found on pets.

How do I deal with fleas biting me in my home?

2 / 11 People are most commonly bitten by cat fleas emerging from pupae and feeding for the first time. Although they cannot survive on people, they can inflict bites with significant skin reactions (Figure 1).

These bites can occur from flea infestations being maintained by the owner’s pets, stray cats or wildlife entering the home, or when people enter homes that have been vacated for long periods with pupae lying dormant.

If people in the household do not own pets and bar entry to other animals entering the home then environmental treatment alone will rapidly reduce the number of bites. This may also be required if the home is invaded by avian fleas from abandoned nests in attic spaces or chimneys.

Pyrethroid sprays containing growth inhibitors are effective, but if the source of the infestation is not clear, whole house fumigation may be required. If pets are present in the home to allow flea reproduction then a multiple-pronged strategy is required.

Adulticide

Using an effective adulticide can prevent egg laying and break the reproductive cycle. Adulticides must kill 100% of fleas before they can lay eggs. Adult fleas can lay eggs within 24 hours, so an effective flea treatment must kill fleas at least within that time. They must also be administered frequently enough to continue to prevent egg laying.

The time after application at which fleas survive long enough in the presence of the product to lay eggs is known as the “reproductive break point”. If the reproductive break point is reached then flea control will fail.

Effective environmental control

3 / 11 Figure 2. Book lice.

Directly reducing the numbers of eggs, larvae and pupae in the environment will decrease the time required to bring an infestation under control. This may be achieved using environmental sprays containing a pyrethroid, such as permethrin or deltamethrin (both for dogs), and a growth inhibitor. Lufenuron can also be used in pets systemically to prevent flea eggs from hatching.

Some adulticide flea treatments, such as imidacloprid and selamectin, will subsequently be shed into the environment, reducing environmental egg and larval contamination. Many spot-on flea products also contain growth regulator S-methoprene to achieve a similar effect. Daily vacuuming of areas frequented by infested pets has also been demonstrated to reduce pupae in the environment.

Flea infestations take at least three months to eliminate – often much longer – with nine-month treatment regimens often required (Dryden et al, 2000). This needs to be made clear to clients so they are prepared for long periods of treatment before fleas are eliminated – and so they do not rapidly become disheartened.

It is also important to establish whether fleas are present at all. Insect life stages have been presented to the author, which owners believed to be parasitic life stages attacking them in the home. Examples are book lice (Figure 2), which look like bed bugs, but are, in fact, free-living insects. They congregate around food bowls, making pet owners sometimes think they are fleas or lice.

Plant seeds (Figure 3) may sometimes be mistaken for flea eggs and flea larvae (Figure 4) are sometimes presented in the belief they are attacking owners. Although this life stage feeds on detritus and flea dirt, it is a sign flea infestation is present in the home.

4 / 11 Adult cat fleas may be identified by their laterally flattened appearance and head combs (Figure 5).

Can ticks infest my home like fleas?

Ixodes species ticks are predominant in the UK and have a life cycle of three years. In temperate climates, each life cycle feeding stage does so only once per year, so takes three years from egg to adult.

The larval stage that feeds in the first year requires small hosts, such as rodents and songbirds. As a result of these factors, it is unlikely Ixodes ticks will establish in UK homes and exposure takes place primarily outdoors.

Figure 3. Plant seed casing.

Dermacentor and Rhipicephalus species have similar life cycles, with the potential to complete them more quickly; in the case of Rhipicephalus, often within one season.

This allows it to potentially take advantage of increased temperatures in central-heated homes and become established in households in a similar way to fleas.

It has not yet formed endemic foci in the UK, but two cases of house infestation have been recorded in south England (Hansford et al, 2015). These cases were from dogs imported from Europe and at least one had been tick-treated before admission.

5 / 11 Nymphs of Rhipicephalus survived and, once established, took more than 12 months to eliminate, despite effective tick treatment of pets and repeated fumigation of the house.

This demonstrates both the importance of checking dogs that have been tick-treated for ticks and also rapid reporting and identification of ticks found in the home.

Macrocyclic lactone use

Can you use milbemycin oxime or moxidectin in collies/related breeds?

Concern exists among veterinary professionals and the public regarding the use of macrocyclic lactones (avermectins and milbemycins) in collies and related breeds.

This is due to these breeds carrying the multi-drug resistance one (MDR1) gene, making them susceptible to ivermectin crossing the blood-brain barrier.

However, licensed macrocyclic lactones – including moxidectin, milbemycin and selamectin – have all been demonstrated to be safe in collies (see individual data sheets).

The safety margin of overdose is narrower in these breeds, however, so it is important to dose accurately and make owners aware of the risk of overdose. They should also be avoided in these breeds where therapeutic indication is to use them at increased frequency, such as weekly use of moxidectin for treatment of Demodex.

Can moxidectin and milbemycin be used together?

The popularity, high efficacy and good compliance with many clients achieved with tablets containing milbemycin oxime and spot-on preparations containing moxidectin, has led to a desire to use them together. However, the two drugs are not licensed to use together in any formulation and, so far, safety data is limited to small case studies. Even if larger studies demonstrating safety were published, without a license it is hard to justify their combined use, given the similar spectrums of activity.

Both being milbemycins, they are very closely related, making the possibility of combined overdose more likely. This is of particular concern in collies and other dogs carrying the MDR1 gene, where macrocyclic lactones already have a narrower margin of safety.

One argument for combined usage is the addition of praziquantel in many milbemycin tablet products. A wide variety of tablets containing praziquantel without milbemycin are available, if moxidectin spot-on preparations are preferred and tapeworm treatment is required.

No grounds exist, therefore, on which combined use can be justified and if there was an adverse

6 / 11 reaction to their combined use then defending this course of action would be difficult.

On evidence, ESCCAP UK and Ireland can, in no way, support their combined use.

European pet travel advice

ESCCAP UK and Ireland receives frequent questions surrounding pet travel. The most common are regarding tapeworm and tick travel requirements under the Pet Travel Scheme (PETS) and confusion around travel to the Republic of Ireland.

Are tapeworm and tick treatments still a PETS requirement?

Tick treatments have ceased to be compulsory for dogs travelling to the UK. This is perceived to have been a factor in the establishment of Rhipicephalus sanguineus in households in south England and in the introduction of babesiosis to the UK.

Although it is likely maintaining the compulsory treatment would have slowed down the introduction of foreign ticks and tick-borne diseases affecting canids, this is not why it was established. Like all compulsory PETS treatments, it was put in place to stop human tick-borne disease entering the country – primarily Mediterranean spotted fever caused by Rickettsia conorii.

While this infection is still present in many European countries, it was felt when the PETS was renegotiated in 2012 human tick-borne disease did not pose a significant enough risk to the UK to continue compulsory treatment.

The removal of the compulsory treatment, while not related to canine disease, may have inadvertently sent a message to pet owners taking their dogs abroad that the risk to their pets had reduced. This is very much not the case and it is vital veterinary professionals continue to impress on owners the importance of using a tick repellent product while abroad. This will help reduce the risk of tick-borne disease, including rickettsial diseases that may be transmitted within hours of attachment (Fourie et al, 2013).

Owners should also check pets every 24 hours for ticks and remove any with a tick hook. It is also useful for a vet or veterinary nurse to check for ticks on the pet’s return.

Compulsory treatment for tapeworm with praziquantel before return to the UK is still in place, but in 2012, was extended to between one and five days before return to the UK. This treatment is in place to protect against Echinococcus multilocularis – a deadly zoonosis carried by foxes and microtine voles. It has been demonstrated, without this treatment, entry of the parasite into the UK would be inevitable (Torgerson and Craig, 2009).

The half-life of praziquantel is short, however, at around 12 hours. This means it is rapidly

7 / 11 eliminated from the body and, as a result, a small window of opportunity exists for infection to occur between treatment and return to the UK. The perverse situation now exists where a client could have a praziquantel treatment for his or her pet in the UK under the scheme, believing this to be adequate protection. He or she could then travel to Europe two days later with likely sub- therapeutic concentrations of praziquantel in his or her dog, before returning to the UK within five days of the original treatment.

For this reason, ESCCAP UK and Ireland recommends a further treatment with praziquantel 30 days after returning to the UK to ensure egg shedding by E multilocularis does not occur. The prepatent period of E multilocularis is at least 30 days, so monthly treatment with praziquantel is also advised while pets are abroad to prevent egg shedding and subsequent zoonotic risk to owners.

Figure 4. Flea larvae.

In continental Europe, epsiprantel has also been used as preventive treatment for E multilocularis. Epsiprantel is a cestocidal drug in the isoquinoline group and is closely related to praziquantel. It has been demonstrated to have high efficacy in reducing and eliminating E multilocularis infection in dogs (Eckert et al, 2001). For the purposes of the PETS, however, praziquantel, rather than epsiprantel, should be used for the following reasons:

It is not licensed for the treatment or prevention of E multilocularis infection. Although it has been found to be highly efficacious, Eckert et al (2001) found half the dogs

8 / 11 treated to have residual worm burdens, posing a potential risk to pet owners and the UK’s E multilocularis-free status. These residual worm burdens have led the American Academy of Veterinary Pharmacology and Therapeutics to class the efficacy of epsiprantel against E multilocularis as “potentially effective”.

Until further studies have been carried out on the efficacy of epsiprantel against E multilocularis then praziquantel will remain the drug of choice for this purpose.

Do tapeworm and tick treatments still apply to the Republic of Ireland?

Compulsory tapeworm treatment is not required if pets are travelling directly from the Republic of Ireland to the UK, but all other pet passport rules apply.

Babesia canis prevention advice

Babesiosis is a common disease found in dogs infected with Babesia canis across mainland Europe. Infected dogs can develop severe acute disease, leading to haemolytic anaemia, secondary organ failure and, in some cases, death.

In February 2016, B canis was reported in three dogs from Harlow, Essex (Swainsbury et al, 2016) and in a fourth dog from the same area in March 2016 (Woodmansey, 2016). The four dogs were from four separate households, had not travelled abroad and not been in contact with dogs that had done so (Woodmansey, 2016).

DNA barcode testing and PCR testing confirmed ticks found on the infected dogs to be Dermacentor reticulatus infected with B canis (Phipps et al, 2016). This suggests there is now an endemic focus of B canis in Essex. D reticulatus ticks were already endemic in Essex and adjoining counties, making the spread of B canis likely now infection is established. Transovarial transmission from tick to tick has the potential to rapidly increase B canis prevalence in the tick population. In addition, movement of infected ticks on mammalian hosts, mechanically in vehicles and on clothes may disseminate it to other D reticulatus populations in the country.

The high levels of publicity in the media, such as Marshall (2016), associated with this outbreak has led to understandable concern from the public and veterinary professionals about potential spread and preventive measures in pets living in south-east England. While increased vigilance is justified and it is likely to spread to adjoining counties, it is limited to a small number of cases, so public fears should be kept in perspective.

Dog owners in Essex, however – particularly in Harlow, as well as in adjoining counties – need to be aware of the potential for B canis transmission. It takes at least 24 hours for B canis to be transmitted, so owners should check their

9 / 11 dogs daily for ticks and remove any with a tick hook.

Ticks found that appear decorated or have festoons (crimping around the edge of the tick to give a “Cornish pasty” appearance) should be placed in a sealed container and taken to a veterinary professional for identification. Veterinary professionals and owners may also send ticks to Public Health England for identification.

Figure 5. Cat flea.

Using a tick preventive product is strongly advised for all dogs in this area. Either a product that repels or rapidly kills ticks should be used and will greatly reduce the risk of disease transmission. No product is 100% effective, however, so dogs should still be checked daily.

This advice is true for the whole of the UK due to the risk of Lyme disease transmission, but is more risk-based. Dogs that have had ticks previously or walk in rural areas, or known tick or Lyme disease hot spots, should also use a tick preventive product and check their pets and themselves for ticks every 24 hours.

In Essex and adjoining counties, dog owners and veterinary professionals should be vigilant for the clinical signs of babesiosis as delay in treatment can be fatal.

Dark red urine, blood in the urine, pale or yellow gums, lethargy, lymphadenopathy and fever are all classic signs of infection.

Conclusion

10 / 11 Some confusion remains among the public and veterinary professionals about domestic and foreign parasite control, both in terms of the risks parasites pose and the drugs available to control them. Concern often exists that advice sought may not be reliable, or be biased.

ESCCAP UK and Ireland remains an independent, expert source of advice on parasite control and is happy to answer any parasite-related questions through its website. In this way, consistent, reliable and up-to-date advice can be disseminated in addition to the CPD, written materials and web-based content ESCCAP UK and Ireland provides.

References

Dryden MW, Denenberg TM and Bunch S (2000). Control of fleas on naturally infested cats and dogs and in private residences with topical spot applications of fipronil and imidacloprid, Veterinary Parasitology 93(1): 69-75. Eckert J, Thompson RC, Bucklar H, Bilger B and Deplazes P (2001). Efficacy evaluation of epsiprantel (Cestex) against Echinococcus multilocularis in dogs and cats, Berliner und Münchener tierärztliche Wochenschrift 114(3-4): 121-126. Fourie JJ, Stanneck D, Luus HG, Beugnet F, Wijnveld M and Jongejan F (2013). Transmission of Ehrlichia canis by Rhipicephalus sanguineus ticks feeding on dogs and on artificial membranes, Veterinary Parasitology 197(3-4): 595-603. Hansford KM, Pietzsch M, Cull B and Medlock JM (2015). Brown dog tick infestation of a home in England, Veterinary Record 176(5): 129-130. Marshall C (2016). Dog owners warned about new tick disease, www.bbc.co.uk/news/science-environment-35815813 Phipps LP, Del Mar Fernandez De Marco M, Hernández-Triana LM, Johnson N, Swainsbury C, Medlock JM, Hansford K, Mitchell S et al (2016). Babesia canis detected in dogs and associated ticks from Essex, Veterinary Record 178(10): 243-244. Swainsbury C, Bengtson G and Hill P (2016). Babesiosis in dogs, Veterinary Record 178(7): 172. Torgerson PR and Craig PS (2009). Risk assessment of importation of dogs infected with Echinococcus multilocularis into the UK, Veterinary Record 165(13): 366-368. Woodmansey D (2016). New tick-borne disease confirmed in UK dogs, Veterinary Times 46(9): 1.

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