giardia faqs
 Do you test for Giardia?
Yes, we test for Giardia, but you must call in advance, mail it on specific days, and follow our mailing instructions. We offer this service to all pet owners, humane or rescue groups, pet stores, breeders, etc. and have special volume discounts.

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 When do I test for Giardia?
Test all puppies, adults, and pets that have diarrhea ASAP. Most veterinarians will treat puppies if positive, or if any pet has clinical signs. Test prior to breeding, buying, or selling dogs.

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 How do you diagnose Giardia?

The GIARDIA TEST@HOME Elisa snap-an antibody-antigen test using a commercial snap test(Iddexx) is most commonly used and much more accurate. Studies examining the reliability of Elisa kits have found them to be over 90% accurate, with relatively few false negatives or false positives.

Giardia is very difficult to diagnose with a microscope, so the fecal smear that is rarely performed any more is unreliable. As a result Idexx has developed an antibody-antigen test, that is reliable, to detect Giardia.  The test needs to be performed on a fresh sample or one that has been frozen (refrigerated) and shipped overnight. This test is reliable, but still not 100% accurate.

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**        GUARDING AGAINST GIARDIA                     Maggie Fisher BVetMed MRCVS


 

The Giardia trophozoite - which is the active stage of the organism - inhabits the small intestine of the dog. It attaches to the cells of the intestine with its adhesive disc and rapidly divides to produce a whole population of trophozoites. As they detach they may be swept down the intestine. If intestinal flow is fast then they may appear in the feces. However, if they have time, they will develop into the inactive, more durable, cyst form of the organism and these will be passed in the feces. The cyst  is more able to survive in the environment than the trophozoite, which is very fragile.

How do Giardia cause disease in dogs?

Like all infectious agents, in order to cause disease Giardia depends on being able to overcome the dog's defense against infection, either by its virulence or by the number of the organisms becoming established. It has been observed that as few as 10 cysts can cause disease in humans. Different animals may respond to infection in different ways, which may be due to different strains of the same Giardia population, with varying levels of pathogenicity. Another explanation for observed differences in the host response to infection is that protective immunity with age and/or exposure. This may be temporarily lost if the animal is stressed or immunosuppressed, for example with corticosteroid treatment.

What is the source of infection for dogs?

The original source of an outbreak may be cysts in contaminated water or the environment. In addition, infected dogs which may be either carriers (ie: show no clinical signs but continue to harbour infection and pass cysts into the environment) or dogs that have diarrhea associated with infection may act as the source. Surveys have shown that about 14% of the adult dog population and over 30% of dogs under one year of age were infected. Once passed, the cysts can survive in cold water for several months.

The cysts are infective as soon as they are passed, unlike other parasites where a lag period is necessary before the organism is infective. The most common route of infection is feco-oral. For example, dogs may accidentally eat cysts as they lick around the environment or lick other dogs' coats (particularly if the other dog has diarrhea). Another major source of infection in human cases is drinking contaminated water. Once eaten, the cyst breaks open in the animals' intestine and releases two new trophozoites to initiate infection. If a dog is left in a dirty environment it may act as its own source of further infections it eats cysts passed in its own feces.

What are the clinical signs associated with infection?

The trophozoites divide to produce a large population, then they begin to interfere with the absorption of food, so faeces from affected animals are typically light coloured, greasy and soft. These signs, together with the beginning of cyst shedding, begin about one week post-infection. There may be additional signs of large intestinal irritation, such as straining and mucus in the feces, even though the Giardia do not live in the large intestine. Usually the blood picture of affected animals is normal, though occasionally there is a slight increase in the number of eosinophils (one of several types of white blood cells) and mild anemia. Without treatment, the condition may continue, either chronically or intermittently, for weeks or months.

How can infection be diagnosed? Order the GIARDIA TEST@HOME Elisa snap-an antibody-antigen test.

Diagnosis is based on demonstration of the infection and the elimination of other possible causes of diarrhea (eg: Salmonella or Campylobacter), Giardia cysts may be observed directly in faecal samples or indirectly using an elisa technique. Direct examination of faeces, using zinc sulphate centrifugal flotation. followed by staining the supernatant with Lugol's iodine, has been found to of extremely variable and less than 15% effective at detecting infection from a single faecal sample. The cyst output is very variable from day to day so the detection rate is not reliable. Faecal examination is the cheapest method but is time consuming and does not produce reliable results.

The GIARDIA TEST@HOME Elisa snap-an antibody-antigen test using a commercial snap test(Iddexx) is most commonly used and much more accurate. Studies examining the reliability of Elisa kits have found them to be over 90% accurate, with relatively few false negatives or false positives. However, the tests are costly.

How can infection be treated?

Infection may be treated using one of a number of drugs. Unfortunately there is no treatment licensed for the control of giardia in dogs, though fenbendazole (Panacur, Hoechst Animal Health) is licensed for treatment of worms in dogs. Treatments from the literature are shown in table 1. Whatever treatment is chosen, it is very unlikely to eliminate 100% of the infection in all dogs. Adaptations that may be made to try to improve the success rate of a treatment regime include extending the duration and dose of the treatment. Care must obviously be taken with this approach to make sure that an adequate safety margin is always maintained. Another approach is to retreat after an interval of one week. Alternatively, repeat faecal samples may be collected one week after the treatment and dogs which are still passing cysts can be identified and treated. It should be recognised that, when treating a large number of dogs, whichever of these treatment strategies is adopted, there may be one or two dogs that remain as carriers of infection that will act as a potential sources of infection in future.

Treatments for Giardias in dogs

Drug Name

Trade Name

Dose Rate

Duration of
Treatment

Metronidazole

Flagyl

25-30 mg/kg bid**

7 days

Furazolidone

Neftin

4 mg/kg bid*

10 days

Tinadazole

-

44 mg/kg once daily

7 days

Fenbendazole

Panacur ***

50 mg/kg once daily

3 days

Albendazole

Valbazen

25 mg/kg bid

2 days

bid

Twice daily

*

Maximum daily dose 200 mg

**

Contra-indicated in pregnancy

**

Licensed for the treatment of worm infections in dogs

How can infection, once present , be controlled?

Once infection is present in a kennels, control may be approached in two ways:-
1. identification, isolation and treatment of infected dogs.
2. mass treatment of all dogs.

Option 1 is only practical where a few dogs in a discrete area have been identified as being infected and where complete isolation is feasible, either within their own block or in a specific isolation block. Such isolation includes segregation of exercise areas and thes animals should be fed and cleaned after all others on the premises, preferably using separate cleaning and feeding equipment and separate staff if possible. Treatment of all dogs should commence on the same day when option 2 is adopted.

Thorough cleaning of all kennel area where infected dogs have access is essential. Once organic debris has been removed, thorough disinfection will help to further reduce the level of environmental contamination and reduce the risk of dogs becoming re-infected after the completion of treatment. Disinfectants containing quaternary ammonium compounds have been found to kill Giardia cysts at the manufacturers' recommended dilutions (dilutions of one disinfectant up to 1:704 were found to be effective at both low and high environmental temperatures). Efficacy of killing is increased by prolonged contact time, therefore disinfectant solution should be left for 20 minutes to half an hour before being rinsed off kennel or run surfaces. Since disinfection of grass runs is impossible, such area should be regarded as contaminated for at least a month after infected dogs last had access.

Introduction of new dogs into the infected area should be avoided until the period of treatment and faecal sample checking has been completed. It should not be overlooked that some of thoe infected dogs may continue to excrete low numbers of cysts even after all treatments and examinations have been completed. It is therefore important that rigorous disinfection is maintained and a careful check is kept on the condition of all treated and introduced animals.

How can infection be prevented?

It is very difficult to prevent entry of an infection that is known to be carried by a percentage of normal dogs into a kennels. However, an initial period of isolation for all new entrants into kennels, for perhaps ten days, would reduce the risk of an infected dog spreading a large number of cysts around the main kennel area. All dogs could be observed and any infection present, which in the case case of Giardia might be exacerbated by the stress of entry in kennels, could be identified and treated before entry into the main kennels.

Dogs should be prevented from access to foul water that may contain large numbers of cysts (ie: river-flooded paddocks).Small numbers of cysts may occasionally be present in the potable water supply but the risk of this being a major source of infection is small.