External Parasites

1. FLEAS

Fleas are very common parasites in the Vancouver area. Most pet owners are only too aware of their presence! The adult flea spends most of its life on the animal… feeding on the animals blood and reproducing. Female fleas can lay up to 40 eggs per day. These eggs fall off the pet into carpets ,cracks and furniture (or if outdoors onto the ground). Within 1 to 10 days the eggs hatch into larvae. These look like fine, dark, wiggly threads about 1/2cm long. The larvae feed on organic debris for 5-11 days before forming a cocoon. It is during the larval stage that they can consume tapeworm eggs and become the intermediate host for the development of tapeworms… more on that later. The cocoon stage protects the flea as it transforms into an adult. This stage (pupa) are very resistant to insecticides. Fleas can emerge as quickly as 12 days or, if conditions are less than optimal pupae can remain dormant in excess of 18 months! It is the insecticide resistance of the pupal stage that has made flea control so difficult in the past. Now products are able to bypass this problem. Once hatched the baby fleas quickly seek a blood meal and the cycle starts anew!

It is recorded that 10 adult fleas can multiply to more than 250,000 fleas in only 30 days!

Given these figures it becomes easy to appreciate the need for prevention. As with many things… “An ounce of prevention is worth a pound of cure”.

Does my pet have fleas?

FleaIf your pet is scratching or has irritated skin it may have fleas. If you have red bites on your feet and ankles… your pet may have brought fleas into your home. Dog and Cat Fleas do not live permanently on humans, however, if a human is handy and a flea is hungry it will not hesitate to take a meal where it can find it.

It is fairly straight forward to check for fleas. You can run a flea comb down your pets back to the base of tail… take care to get right through to the skin. You may see live fleas or perhaps just the excrement left behind where it took its meal. Flea excrement looks much like finely ground pepper. As it is a digested blood meal, if you put some on a damp white tissue you can see that as it dissolves it leaves a rust coloured stain on the tissue. Another method is to put your pet on a clean light coloured surface and give it a good rub in all directions… really stirring up the hair coat. If you then see black specks on the light coloured surface and these are positive for the tissue test… then your pet has fleas. In some cases the flea infestation will be great enough that you can see the little devils scurrying about on your pet. They are usually most visible at the base of the tail and in the groin area.

Flea life cycleThe flea life cycle

Effective Flea Control is based on the life cycle of the flea.

STAGE % of TOTAL POPULATION
ADULT 5
PUPAE 10
LARVAE 35
EGGS 50

Eggs are what make up the largest portion of the population. If they are not laid in the first place, or if they are prevented from hatching, flea control can be accomplished.

Fleas and Disease

FLeas are one the primary initiators of skin disease in pets. These blood sucking parasites inject minute amounts of saliva when they take a blood meal. This results in an irritation and causes your pet to chew and scratch. This damages the skin and allows for secondary bacterial infections to occur. If your pet is scratching be sure to check for fleas! Fleas will also take a meal from humans, resulting in an itchy swelling where the bite was inflicted.

Fleas are the intermediate host for tapeworms. Tapeworm egg cases are passed with an animals feces or directly from the anus. They dry out and release tapeworm eggs into the environment. The larval stage of the flea ingests the eggs and an intermediate stage of the tapeworm develops in the growing flea. When your pet is itchy it chews at itself and ingests the flea, along with its baby tapeworm. The tapeworm then completes its lifecycle in your pet’s intestine.

Fleas live on blood and in severe infestations can consume enough blood to cause anemia. Animals that are very young, old or debilitated are at greater risk for debilitating blood loss.

Fleas are the vector for Bubonic plague in humans.

Flea Control

Fleas can be found on the pet and in its environment. As a result an effective flea control program must address both the pet and its premise. The key to understanding effective control, or treatment, is knowledge of the flea lifecycle. In the past flea control was directed towards removing adult fleas from the pet. This was not effective because the pre-adult stages matured and the pet was reinfected from its environment. To address this products, such as adulticide collars, sprays, mousses and dips, with residual actions were developed. This helped the situation with respect to the pet, however, they did not address the environmental source and were work intensive to maintain. As a result these methods were still not very effective. People became aware of the importance of environmental (premise) control and products became available for treating the home and yard. This, combined with regular on pet treatment with residual effect products made great strides in the battle against fleas. Compliance was often a problem as it was a work intensive approach and many did not like the idea of insecticides on their pets and in the home. In any case it did not address the insecticide resistant pupal stage of the flea lifecycle. As an alternative to topical insecticides oral products became available. These early products, such as Ectoral and Proban, were based on inhibiting enzymes that were common to both the flea and animals. As a result inadvertent overdose, or use during medical compromise, could result in injury to the pet as well as the flea! Another approach was the use of topical products, such as ProSpot, that were dropped onto and absorbed into the skin. These products were potentially hazardous to the pet and those applying them. Instructions were to apply it in a well ventilated room wearing rubber gloves, and to avoid handling the pet for some time afterward! Needless to say these products were not the answer to safe flea control.

It became apparent that failure to control fleas would result unless the pet and the environment were treated simultaneously, with products that were safe, effective and user friendly. These products are now available and flea control is no longer a mammoth and hazardous task. Revolution (selemectin), Comfortis (spinosad), Advantage (imidacloprid), Program (lufenuron) , Sentinel(leufenuron & milbemycin) , Ovicollars (precor IGR), Capstar (nitenpyram) and Frontline (fipronil) are making history of flea infestations! As yet Frontline is not approved for use in Canada. Novartis products (Program, Interceptor and Sentinel) are not currently available.

Ovicollars release an Insect Growth Regulator (IGR), a juvenile growth hormone unique to insects, that prohibits immature fleas from developing into adults. These soft pliable collars are effective for 8 months on dogs and 11 months on cats. They do not kill adult fleas but are very effective at breaking the flea lifecycle and stopping flea infestation. In animals with Flea Allergy Dermatitis, this collar combined with Advantage works very well. With the advent of products such as Revolution, Comfortis and Triflexis these collars are rarely used.

Advantage is a topical flea adulticide for dogs and cats. It interferes with nerve transmission in adult fleas and a single application is effective for about 30 days. It is packaged as a premeasured dose that is applied along the back. It quickly wicks over the body surface resulting in a 98-100% flea kill in 24 hours. This product does not require the flea to take a blood meal before being effective. As a result it can kill the flea before it bites. This product can be safely combined with Insect Growth Regulators (IGR), such as Ovicollars or Insect Developement Inhibitors (IDI), such as Program to form part of a comprehensive flea management plan.

Program, like the Ovicollar, acts by inhibiting immature flea development into adult fleas. It is available for dogs and cats in a safe effective oral form. A single oral dose lasts 30 days. A longer acting injectable form is available for cats. One injection is effective for 6 months.

Sentinel functions like Program for flea control and also offers protection against heartworm, hookworm, ascarids and whipworm. It is a once monthly oral preparation. This product is not currently available.

Revolution is a comprehensive parasite product. It is applied topically and it passes through the skin to act internally. It protects against many parasites including adult and immature stages of the flea, several mites, lice, heartworm plus acarids, hookworms and whipworms. It is quickly increasing in popularity as it is safe, effective, easy to use and has a broad spectrum of protection.

Comfortis is an oral flea control product that is safe and effective. Triflexis is a broader spectrum oral product that addresses both internal and external parasites.

At WBVC Revolution (a topical product) and Comfortis (an oral product) are the most popular parasite management products. They are easy to administer, safe and effective.

Shampoos, adulticide collars, sprays, mousses and powders are still available and can be useful under certain circumstances. They contain such ingredients as pyrethrins, pyrethroids, carbamates and organophosphates.

Natural insecticides are available, however most claims of effectiveness are purely anecdotal. The include ingredients such as rosemary, wormwood, pennyroyal, eucalyptus, citronella and diatomaceous earth. Products derived from from citrus pulp such as d-limonene and linalool have been marketed but have also been implicated in some cat deaths! Although safe Brewer”s yeast, thiamine and garlic have not proven effective in clinical trials. Avon Skin So Soft, in diluted form (5%), has proven to act as an insect repellent but does not kill fleas.

Premise and environmental control products are useful in affecting a rapid start when combating an existing flea infestation.

We recommend you contact your veterinarian prior to purchasing any flea control products. The appropriate product(s) will depend on the species, age and health of your pet combined with the severity of the flea situation and your pets lifestyle. This information can often be obtained over the phone at no charge. Salespersons in pet store outlets do not have the knowledge of a trained veterinarian. Seek the products that are best suited to your pet and your situation.

Tick life cycle2. TICKS

All ticks are bloodsucking parasites. Although there are several different types of ticks, each has four stages of development in its lifecycle. These four stages are: the egg, the six-legged larva, the eight legged but sexually immature nymph, and the eight legged sexually mature adult. The types of ticks vary in how many different host animals they visit during this lifecycle. Some one host ticks go from larva to adult on one host animal, others drop off their host after the nymph has fed to seek another host for the remainder of the lifecycle… these are termed two host ticks. There are also three host ticks whose larvae and nymphs drop off after feeding. This cycle can span several weeks to two years.

Two and three host ticks can spread disease interstadially ; that is the disease organism is carried by the tick as it transforms from one developmental stage to the next. One host ticks transmit disease by passing organisms from from an infected adult female tick to her progeny transovarially.

Tick populations and the diseases associated with them vary demographically. In the Pacific Northwest Lymes disease is the most prevalent concern. This can be treated with antibiotics. There is also a vaccination available for prophylactic control. Elsewhere ticks are associated with tick paralysis, Babesiosis, rickettsial diseases, viral diseases and bacterial diseases.

Pets most at risk are those exposed to grassy and woody areas populated by wild animals.    You may see nymphs or adult ticks on your pet as both phases feed on animals. The unfed ticks come onto your pet looking like a small crawling bug… the immature stages being smaller than the adults. Once attacked to your pet and feeding they swell up until they look first like a dried raisin and then like a well plumped one.When they finish feeding they leave and inflamed area where they penetrated the skin.

            

 

Tick Control In the past tick control was retroactive. If your pet contracted ticks you could use a concentrated flea product such as Sendran Dab-on directly on the tick. A tick can be manually removed by grasping it very close to the skin with a pair of tweezers and gently rotating. However, if the tick is broken mouth pieces are left in the skin a crusty sore may develop. If you wait a few days until it finishes gorging itself, the tick will fall off on its own.

Products such as Preventic collars, Ovitrol Plus collars, K9Advantix (imidaclopromide & permethrin) and Frontline are formulated to kill ticks before they become firmly attached. Frontline is not approved for use in Canada. Unlike the IGR Ovicollar these collars contain ingredients that are potentially hazardous… Preventic (Amitraz) and Ovitrol Plus (Tetrachlorvinphos, an organophosphate). The animals age, health and lifestyle should be considered in order to determine if these products are required, and safe, for your pet. There are more and more products becoming available. A veterinarian should be consulted prior to use.

3. MITES

Mites are minute arachnids requiring magnification for identification. They can affect most species, causing inflammation and irritation of the integument. Some mites spend their entire lifecycle on the host while others can live for several days off the host. At this time mites are dealt with reactively rather than proactively. It is the pet owners responsibility to detect a possible problem, however effective treatment requires an accurate diagnosis.

Surface feeding mites occurring in family pets in Pacific Northwest include:

OTODECTES. These ear mites are seen primarily in cats. They are spread from cat to cat. These mites cause severe inflammation of the ear canal. The ears are itchy and the cat will scratch the ear, sometimes to the extent of causing open sores in the skin behind the ear pinna. The canal itself becomes filled with dark gritty debris. Treatment involves irradicating the mites plus cleaning and medicating the ear canal. Topical ear medications,  injectable ivermectin or products such as topical selemectin can be used to kill ear mites. These mites can live for a short period of time outside of the ear canal on the cat and in the environment. In cases of persistent reinfection it may be necessary to treat the premise but with newer products this is generally not required.

PSOROPTES. These are ear mites of rabbits. If left untreated they cause heavy light coloured crusting of the ear canal. Treatment is similar to that in cats.

DEMODEX. These mites affect dogs and on occasion cats. These host specific parasites live deep within the hair follicles and glandular ducts. They are transmitted to nursing pups via direct contact with the dam soon after birth. Most healthy animals harbour small numbers of these mites. In some dogs the immune system does not keep their numbers in check and the mites multiply to numbers that cause clinical disease; Demodectic mange. This is evidenced by patchy areas of hair loss often on the face and forelimbs. The localized form can become secondarily infected with Staphylococcal bacteria. This generalized form can cause severe illness. In some cases of localized demodex the body will eventually develop an adequate immune response and spontaneous remission will occur. In the past treatment has been difficult, hazardous and not terribly effective. Although an “off label” use, oral Ivermectin administered for 60-90 days appears to be a relatively safe, effective and easy way to treat demodex infections. Other products such as Advantage Multi are also used to control this parasite. Because it is thought that animals suffering from Demodectic Mange are immuno-compromised, it is advisable to spay/neuter them in case there is an inherited trait.

CHEYLETIELLA. Often called “walking dandruff” these mites cause inflammation, itching and a mealy dandruff especially along the back. It can occur in many species, but is seen most often in rabbits and dogs. These mites can live for short periods of time off the host. Treatment involves the use of topical or injectable insecticides. On occasion premise treatment is required.

SARCOPTES. Sarcoptic mange is intensely itchy and can be passed between dogs and humans. These mites often cause crusty lesions on the ear tips and red itchy spots on the ventral abdomen. Although they can be treated with topical products, injectable insecticides are very effective. This form of mange is rarely seen in our practice.

4. LICE

Lice are tiny insects, about 3mm long, that spend their entire lives among the hairs of their hosts. They are very host specific and do not live off their host.  As with mites there are sucking lice (Anoplura) and biting lice (Mallophada). Their eggs (nits) are firmly attached to the hosts hair. The lifecycle, from egg through several immature stages to adult, takes from 2-3 weeks. Lice can be readily treated with most insecticidal products. They are seen occasionally urban practice and can be controlled with topical flea products.


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