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Front Page : Library : Giardia - A GI Parasite
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Giardia - A GI Parasite with Many Faces Anne Zajac, DVM, PhD Michael Leib, DVM, DACVM Andrew Thompson, BSc, PhD Lond, DIC April 7, 2002
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----- Transcript of the Conferencing Room "#VINEvents"
GingerSanders: Welcome to Rounds! Tonight's topic is Giardia: A GI Parasite with Many Faces Sponsored by Fort Dodge Animal Health. A quick reminder for those of you who are pre-registered and participating in the course this for CE credit, please read all of your email from us. To start out this evening, I know a lot of you took the initiative to go ahead but I'd like everyone to introduce themselves with their first and last names, city, state and number of vets in their practice. I'll start... Ginger Sanders, Stafford Kansas VIN Staff GA Everyone. Just go ahead and chime right in. GingerSanders: One other comment -- if you don't get to ask your question or say what you want, don't get the answer you were expecting, or want to expand upon a topic -- bring it up on the message boards :) We love BOARD MESSAGES and can go into much greater depth there :) MESSAGE BOARDS are open to all who are officially registered for the course and other VIN members. The transcript of the session will be available in the event library in a few days. And we will mail it to all nonmembers who gave us their email address "when they came in the door." OK - let's have FUN! And, I'll turn things over to Dr. Kathy James to introduce the instructors. GA KathyJames: Welcome all to Giardia: A GI Parasite with Many Faces. The session this evening is presented by: Anne Zajac, DVM, PhD.
Dr. Zajac is on the faculty of the Virginia/Maryland Regional College of Veterinary Medicine at Virginia Tech in the mountains of southwestern Virginia. She teaches and does research in parasitology and supervises the Parasitology Laboratory in the Veterinary Teaching Hospital. Dr. Zajac lives in the country with her family, some sheep and several Great Pyrenees livestock guard dogs. AnneZajac: Good evening. KathyJames: Michael Leib, DVM, DACVM
Dr. Leib is a professor of small animal internal medicine at the Virginia Maryland Regional College of Veterinary Medicine at Virginia Tech in Blacksburg Virginia. As a regional college, they accept students from both Virginia and Maryland. The College has a stand-alone equine hospital in Northern Virginia at Leesburg. They also have an academic department at College Park Maryland at the University of Maryland (2002 mens NCAA basketball champions) J!!! Dr. Leib has a nine-year-old daughter (who still wants to be a veterinarian) and a wife who is a veterinarian in private practice. Our home is shared with 2 dogs, 4 cats, 4 horses, 1 rabbit, 2 goldfish, 2 fire-belly toads, and 2 very exciting Hermit crabs! Dr. Leib enjoys road biking through the beautiful mountains of Southwest Virginia, hiking on the Appalachian trail, and down hill skiing in Colorado. MichaelLeib: Hello all welcome to beautiful Blacksburg, VA KathyJames: Andrew Thompson, BSc, PhD Lond, DIC Dr. Thompson is Professor of Parasitology in the Division of Veterinary and Biomedical Sciences, Murdoch University, Western Australia, and heads the WHO Collaborating Centre for the Molecular Epidemiology of Parasitic Infections. He has a 19-year-old daughter who is studying conservation biology and wants to be a Zookeeper and a 22 year old son who is with the Australian Army in East Timor. We thought most of you here tonight might not know much about Western Australia, where Dr. Thompson is from. But it is the largest and most beautiful State in Australia; it has most of the resources in terms of minerals and agriculture. However, it is the least populated which is great because the beaches are never crowded. SE Asia is only a few hours away (Singapore, Bali etc). WA also produces the best wine, particularly in the Margaret River region in the south west (his slight bias). The climate varies from tropical in the north, arid desert in the middle to Mediterranean in the south west wet mild winter and hot dry summer. At the moment in Perth which is in the south west, it is early autumn with clear blue skies and temps in the mid-to-late 20'sC. So, now that you're all wishing you were in Western Australia on vacation. RCAndrewThompson: G'day everyone from Perth, Western Australia KathyJames: I have one more item important item before we get rolling. And that is to say a big thank you to Fort Dodge Animal Health for their generous sponsorship of this event! GA AnneZajac: It's nice to see so many people here tonight KathyJames: I think the best place to start tonight is with a bit of overview about the Giardia organism. Perhaps Andrew can begin with a little bit of biology of Giardia. Andrew, GA RCAndrewThompson: Giardia is a flagellated protozoan that morphologically is very distinctive because it has 4 pairs of flagellae, two nuclei that often give the appearance of 'eyes' staring up at you when looking at Giardia down the microscope. It also has a ventral sucking dish that it uses to attach to the wall of the small intestine. It is not an invasive parasite but can quickly build up large populations that cover the surface of the anterior small intestine. During the course of infection, usually within the first 5-7 days, parasites will encyst and move posteriorly down the gut to be voided in the feces as resistant cysts. The cysts are capable of surviving in the environment for extended periods if kept moist and not exposed to high temperatures. The life cycle is direct with infection occurring following the ingestion of viable cysts. GA KathyJames: Thanks Andrew. As a follow up to that, how many strains of Giardia are there? GA RCAndrewThompson: During the course of infection, usually within the first 5-7 days, parasites will encyst and move posteriorly down the gut to be voided in the faeces as resistant cysts. The cysts are capable of surviving in the environment for extended periods if kept moist. Within the major species infecting mammals (G. duodenalis = G. intestinalis), there are at least six. Two of these are definitely zoonotic and are usually referred to as A and B. They infect humans as well as other mammals including dogs, cats and livestock. In addition, there are at least four strains that appear to be host-specific; to dogs, cats, livestock, and rodents. Thus pets may be infected with either zoonotic or their own Giardia strains, the former being of public health significance. You might be interested to know that we have just done a study on the epidemiology of Giardia infections in children in day care centers in Perth. Of the two strains found, those in Group B were most common and statistically there was an association between the presence of diarrhea and infection with strains in group A! The majority of children with strain B showed no clinical signs. How this relates to infections in pets we have yet to determine. GA KathyJames: I think we should talk next about transmission. What's the most common route of transmission? Andrew, GA RCAndrewThompson: Transmission can be direct, via host-to-host contact, or indirect if housed/exposed to a contaminated environment (kennels/cattery etc), or via contaminated water or food. If the VIN staff would turn the moderation off for me, I have a question that I'd like to ask the participants. Because of the big crowd, this first question will be for people born in April, May and June to answer. Everyone's going to get the chance to participate at some point tonight, but we need to break the big crowd up into groups. So, the question is what season of the year, do you diagnose most Giardia cases? ...a. spring ...b. summer ...c. fall ...d. winter RCAndrewThompson: Please answer a, b, c, d give us a sense too of where you are: Eastern US, Midwest US etc. So, Apr, May, Jun, birthday people, GA, type fast GingerSanders: Responses
_AskAQuestion: how long can it persist in a moist environment, ie, what is an "extended period"? RCAndrewThompson: extended periods could be several weeks if temps moderate - low 20's C and moist AnneZajac: most people I speak to here seem to have the greatest problems in summer and I see many would agree with that. KathyJames: Thanks. KathyJames: Before we leave the topic transmission, I have what I suspect is a common question. Anne, would you take this one? If your dog or cat has Giardia, does it mean you should test your water? Anne, GA AnneZajac: Many of the calls that I get from concerned pet owners and also from practitioners make it clear to me that most people assume that Giardia is always transmitted by water. Our students frequently blame a pond with beavers in the beautiful national forest around Blacksburg as the cause for Giardia infection in their dogs. It's certainly true that Giardia can be very effectively transmitted by water and there are have been some dramatic outbreaks of infection. However, it is a mistake to assume that every infected animal must have had a drink of Giardia contaminated water. There are many examples of transmission of human Giardia infection in the context of daycare centers where merely direct contact of one infected individual with another transmits infection. We have done experimental Giardia infections here at Virginia Tech and have seen transmission of the parasite to uninfected dogs in a kennel situation where the water certainly wasn't infected. When infected animals are going through the peak period of shedding cysts, millions of cysts are contaminating the environment. Close contact with an infected animal can easily lead to infections in others. So, while an infected dog or cat may have been infected by drinking water with cysts in it, that fact alone shouldn't lead to a concern in owners that their water supply is contaminated. In a rural or semi-rural location like the one here in Blacksburg where many people have individual wells rather than being part of a municipal water supply, there may be concern about contamination from farm animals and wildlife. If human family members are infected as well, a test of the well water may be necessary. Testing of water samples for Giardia is not routinely performed because it isn't as easy as culturing for bacteria. Typically, the sample will be tested for fecal coliform bacteria. If they're present it is reasonable to assume that Giardia cysts may also be present in the water. GA KathyJames: Thanks Anne, I think this is a good place to stop for questions about transmission. If you've got questions on this and haven't sent them to AskAQuestion yet, please do so now. _AskAQuestion: What is the lowest temperature that Giardia can survive at? RCAndrewThompson: cysts can survive for 7-14 days at 4C/39F _AskAQuestion: "?"How long can it persist on the coat of a dog? AnneZajac: I don't know exactly how long they survive on the dog's coat but I believe it is long enough to cause reinfection since bathing dogs after treatment seems important in eliminating the parasite _AskAQuestion: what is the risk from birds, especially wild birds? RCAndrewThompson: birds are usually infected with their own 'strains' of Giardia but can also be passive carriers of zoonotic Giardia _AskAQuestion: How prevalent are "quiet" asymptomatic carriers that become activated when the animals immune system is compromised? AnneZajac: Some animals appear to be persistently infected or else repeatedly reinfected and can continue to contaminate the environment without ever showing disease, they may develop signs again if they become immunosuppressed _AskAQuestion: We sometimes see infections in indoor-only cats - where are they getting it from? RCAndrewThompson: indoor cats could get Giardia from toddlers nappies! KathyJames: Let's turn now to clinical signs. Mike, would you address the common clinical signs associated with Giardia infection? Mike, GA MichaelLeib: The most common manifestation of infection in dogs and cats is no clinical signs. Most asymptomatic dogs and cats will spontaneously clear the infection. When clinical signs occur, acute mild diarrhea is the most common manifestation. Less commonly, severe diarrhea with dehydration can occur. Chronic small bowel diarrhea would be the next most common manifestation. Finally, chronic large bowel diarrhea, acute vomiting and chronic vomiting may occur rarely. Andrew, anything to add? GA RCAndrewThompson: Just wanted to add that "no clinical signs" is our experience in Australia too regarding the most common manifestation. GA _AskAQuestion: How long after ingestion do signs of diarrhea show up? MichaelLeib: It would average about 5-7 days KathyJames: Thanks. Because when they do have signs, acute diarrhea is the most common presentation, perhaps this is a good place to have a quick review of the other causes. What is the differential diagnosis for acute diarrhea in dogs and cats? Mike GA MichaelLeib: I think this is a pretty good list: Giardia ...Dietary indiscretion ..Hookworms, Roundworms, coccidia ...Foreign body ingestion ...Adverse drug effects ...Hemorrhagic gastroenteritis (HGE) ...Parvovirus infection ...Toxic ingestion ...Coronavirus infection ...Intussusception GA KathyJames: As a clinician, what is the initial diagnostic approach you take to the problem of acute diarrhea? Mike GA MichaelLeib: The initial step in evaluation of cases with acute diarrhea is to distinguish between self-limiting and life-threatening causes. Most cases are self-limiting and can be diagnosed with a thorough history, careful physical examination, and fecal examination. Life-threatening cases may be associated with some of the following findings: ...frequent diarrhea, ...moderate to severe dehydration or abdominal pain, ...frequent vomiting, ...or systemic signs such as fever, icterus, lymphadenopathy, coughing, nasal discharge, or dyspnea. Puppies and kittens, especially if unvaccinated, should be suspected of having a life-threatening infectious disease. Animals suspected of having a potentially life-threatening problem should receive: ...fecal examinations for parasites, ...complete blood count, ...biochemical profile, ...urinalysis, ...and survey abdominal radiographs. Additional procedures may be necessary to confirm specific disorders. GA _AskAQuestion: how long for asymptomatic infections to clear? RCAndrewThompson: in our experience dogs can harbour giardia for up to 8 months KathyJames: We're going to talk next about specific diagnostic procedures for Giardia, but perhaps now is a good time to take any questions on clinical presentation and the initial diagnostic approach. GA RCAndrewThompson: The best (in terms of detecting infection but not necessarily the most accurate) way to diagnose Giardia infection in dogs and cats is microscopy following zinc sulphate concentration. However, because Giardia cysts are shed intermittently in the faeces, at least three faecal samples collected over a 5-day period should be examined. Copro-antigen tests have the advantage that antigen will always be present in the faeces of an infected dog or cat, but in our experience such tests are better for detecting infection in humans than dogs or cats. The results of a study we have just completed in Australia might be of interest. Microscopy, PCR and the Giardia CELISA, coproantigen Test were used to determine the prevalence of Giardia in 40 faecal samples obtained from domestic cats in the Perth metropolitan area. A prevalence of 5, 80 and 60% were found by the tests respectively. The results show that more sensitive techniques such as PCR may be necessary, and may yield more reliable results, in the detection of low levels of Giardia in domestic cats. It also suggests that cats, and perhaps dogs too, may harbour very low levels of Giardia that appear to be relatively 'dormant' in terms of cyst excretion. Obviously much more work to do on this aspect of the parasite's epidemiology! Anne, would you like to add to the topic of diagnosis? GA AnneZajac: Many practitioners still use a direct smear for detection of Giardia. The disadvantages of this test are that it isn't very sensitive (you only use a very small amount of fecal material) and it really is only good for the motile trophozoites. There is so much debris in the feces that the nonmoving cysts are difficult to see. Trophozoites are only sometimes present in diarrheic feces, but not always. They are never present in normal stool so only doing a smear would miss carrier animals or ones that only have intermittent diarrhea when you get the sample on a normal day. More sensitive tests than the direct smear are the fecal flotation procedures and the ELISA tests for fecal Giardia antigens. GA _AskAQuestion: How "fresh" is a fresh sample of feces needed for giardia diagnosis RCAndrewThompson: fresh should not have been in the environment for longer than an 1 hour but can be kept at fridge temp for two-three days _AskAQuestion: should you freeze the fecal samples? AnneZajac: don't freeze, just refrigerate _AskAQuestion: Can you visualize cysts and/or giardia at 100X AnneZajac: yes, you can get a sense they are they at 100x then use the 400 to confirm KathyJames: OK, as promised, let's talk next about getting the specific diagnosis. I think the question everyone has is ...Oops, forgot one question Anne, would you elaborate a bit more on these procedures? GA AnneZajac: Flotation procedures destroy Giardia trophozoites in almost all samples and so you are looking for the cysts in flotation tests. Cysts are present in feces much more frequently than trophozoites so this is a much more sensitive test than a smear. However, fecal flotation procedures are not equal when it comes to diagnosing giardiasis. Some of the most commonly used flotation solutions (sodium nitrate, sodium chloride for example) quickly distort the cysts, making them much more difficult to identify. Way back in 1939, a 33% zinc sulfate solution was recommended for detecting protozoan cysts and worm eggs in human feces. It also works wells for small animal samples. This 33% zinc sulfate solution is more sparing of Giardia cysts so they can be easily identified. Although, they are small, Giardia cysts are not hard to find with a little practice. There are some good images of both trophozoites and cysts at the CDC website: http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/G iardiasis_il.htm Okay, we were talking about 33% zinc sulfate solution. It also recovers other common helminths of dogs and cats. It is the routine fecal solution we use for small animal samples in the Parasitology laboratory of the Veterinary Medical Teaching Hospital at Virginia Tech. It is important that the zinc sulfate flotations be performed as a centrifugation procedure. We recently did a study here (that will appear in the next few months in the AAHA journal) in which we compared the recovery of Giardia cysts in zinc sulfate flotation tests. We compared ZnSO4 solution in a standard bench top test (where you let it sit in a pill vial or test tube on the bench for 5 or 10 minutes) with zinc sulfate in a centrifugation procedure. When we tested 50 canine fecal samples, our centrifugation procedure detected 16 Giardia positive samples whereas the bench top incubation detected only 2. GA KathyJames: Thanks Anne. Okay, on to ELISA tests. Anne, GA AnneZajac: Several ELISA tests are available for detection of fecal Giardia antigen. These tests were developed for use in humans but are also being used for dogs and cats. The sensitivity of these tests in dogs and cats has not been extensively tested. We found at Virginia Tech some years ago that the ProSpect (r) Giardia test gave similar to slightly better results compared to a single fecal flotation procedure. So I think there should still be some more work to validate these tests for small animals. A test conducted at Cornell found similar results. In a recent study performed at Kansas State University the ProSpect Giardia rapid Assay test showed considerably lower sensitivity than the zinc sulfate flotation procedure. The advantage of the fecal ELISA is that it doesn't take a trained microscopist to read it. This is a huge plus for the folks in labs testing human samples because parasitology is usually not a big part of their job. A disadvantage is that you will probably still need to do a fecal flotation procedure to determine if other parasites are present. Also, the ELISA test works best in a situation where you have a commercial lab nearby to send the samples to. If you try to keep the kit in your own hospital you may not have high enough demand to use all the tests before the expiry date, which will increase your costs. GA _AskAQuestion: Will cysts and trohpozoites be present in the same sample? RCAndrewThompson: yes you can find cysts and trophozoites in the same sample especially in cases with diarrhea _AskAQuestion: Back to the microscope id: clarify, please: 10x, then 40x - not 100x implied as oil emmersion for identification, right? just in case there is any confusion--when I say 100X I mean the 10X lens times the 10X in the eyepiece, not the 100X oil immersion lens not ignoring all the questions we are not getting to.... we are skipping those we think are covered later. if your ? is not addressed pls ask on the message boards. thanks! ga KathyJames: Andrew, any additional comments on ELISA for diagnosis? GA RCAndrewThompson: Apart from the expense - a good alternative to Zinc sulphate. GA KathyJames: Thanks. Anne, anything else to add on what's the best diagnostic test? GA AnneZajac: At one time duodenal aspirates for trophozoites were thought to be a highly sensitive test, but we did not find them to be very sensitive in a study we did at Virginia Tech. If endoscopy is being performed anyway, a duodenal sample should be collected for examination for trophozoites, but it is unnecessary to perform duodenoscopy merely for the purpose of collecting a sample for Giardia diagnosis. Mike, anything to add? GA MichaelLeib: Duodenal aspiration is worthwhile during endoscopy. It is a fast, inexpensive, and simple test to perform. Rarely, we find Giardia when a fecal examination has been negative. GA KathyJames: Thanks Mike. Anne, with all that background in mind, can you do good tests for Giardia in a busy veterinary practice? GA AnneZajac: Absolutely. But first I have a question to ask you. Because we have a large crowd, we will make this a question for folks with birthdays in October, November and December. The VIN staff are going to turn the moderation off. So, let me ask what test you are already doing for Giardia. ...a. direct smear ...b. benchtop fecal flotation ...c. centrifugal fecal flotation ...d. ELISA Oct, Nov, Dec birthday folks, GA GingerSanders: Responses
AnneZajac: I hope I can persuade you to do a centrifugation technique if you aren't already doing it There is no reason you can't do a good job of detecting Giardia in your practice laboratory. If you have a diarrheic sample, the first thing you should do is a direct smear. Mix a small amount of fresh diarrheic feces with a drop of normal saline and look for trophozoites. The trophozoites can be identified by their rapid "falling leaf" motion and concave ventral surface. If the trophozoites are caught up in mucus you may only see the flagella moving. Trichomonads are the only other motile organism similar to Giardia, but they have a different kind of rolling movement and an undulating membrane along one side. If you find trophozoites on a direct smear you're all set. If you don't, you can't rule out Giardia by any means. OK, here comes the part that may seem too much like a recipe in a cookbook. I do want to mention the details of doing this test properly because, in talking to practitioners, it's clear to me that many practices are reluctant to change the way they do fecal exams, even though they will improve their recovery of all parasites, not just Giardia. If you have a negative diarrheic sample or a formed stool sample, use a zinc sulfate centrifugal flotation procedure. Mix a teaspoonful of feces with about 15 ml of a 33% solution of zinc sulfate (specific gravity 1.18) in a cup. Strain the mixture through a tea strainer, cheesecloth or anything else that will get out the big lumps. Pour the mixture into a centrifuge tube and add additional zinc sulfate if necessary. Centrifuge for 3-5 minutes at 1500 rpm. If the centrifuge rotor is free-swinging, additional zinc sulfate is added to the tube to create a meniscus, a coverslip placed on the tube and the tube is spun with the coverslip in place. The coverslip can be transferred to a microscope slide for examination after centrifugation. Many practice laboratories have a centrifuge with a rotor that is fixed so that the tubes go in at an angle rather than straight up and down. No problem. Centrifuge tubes should be filled as full as possible without spilling when placed in the angled rotor. After centrifuging the tube, the top layer of fluid can be gathered in 2 ways. 1) A microbiological loop or the rounded bottom of a small glass tube (such as an empty blood collection tube) can be touched to the surface of the liquid in the tube after centrifugation. The loop or tube is then touched to a microscope slide and a drop or two of fluid is deposited. A coverslip should be added and the slide examined. 2) Alternatively, the tube can be removed from the centrifuge after spinning and then placed in a test tube rack. Additional flotation solution is added until a reverse meniscus forms and then a coverslip is placed on top. The tube is allowed to sit for an additional 5 minutes to allow parasite eggs to float the rest of the distance to the coverslip. The coverslip is then removed and placed on a microscope slide. Centrifuges commonly found in veterinary practices also provide adequate force for centrifugal flotations. As a general guideline, centrifuging a tube at the same speed used for spinning blood or urine should be sufficient for flotation procedures. Lugol's iodine may be added to the centrifuge tube or slide to stain cysts and make identification easier. With experience, cysts can be identified without staining. Cysts are small, about 12 microns, but they have distinct internal structures and are quite refractile. An experienced slide reader will be able to tentatively diagnose them using the 10X scanning lens. The 40X lens can be used for confirmation. The structure most commonly confused with Giardia is yeast. Most yeast are approximately half as large as Giardia cysts and contain less distinct internal structures. If you use barium sulfate, several proprietary antidiarrheals, or an enemas before collecting the fecal sample, recovery of cysts may be reduced. BTW, zinc sulfate can be purchased commercially in bottles where you just need to add water up to a line in order to have approximately a 33% solution. Synbiotics Corp., as an example, sells zinc sulfate this way. We made up several bottles as directed and found that the specific gravity was never exactly 1.18, which is what you are aiming for. Veterinarians aren't really trained to think about quality control for fecal exams, but I would encourage you to spend $20.00 on a hydrometer (available from scientific supply companies) that will allow you to test the specific gravity and make sure it is correct. GA KathyJames: Thanks Anne. Perhaps we should see if there are any questions on these techniques? GA _AskAQuestion: can't one simply use a refractometer like for urine sample to determine SG of solution? AnneZajac: no it doesn't go high enough _AskAQuestion: Is there an enrichment media for Giardia culture similar to the product used for Trichomoniasis in cattle? AnneZajac: no, not a this time KathyJames: It's probably time now to treat. Mike, how do you treat an infected dog or cat? GA MichaelLeib: Treatment can include either metronidazole 50 mg/kg sid for 5 days or fenbendazole 50 mg/kg sid for 3 days. Neurologic toxicity can occur with metronidazole. Clients should discontinue the medication at the first signs of ataxia, tremor, or seizure. Limited study suggests metronidazole is effective in approximately 75% of infected dogs. Although fenbendazole is very effective in experimental dogs, no data is available in clinical patients. Because we're talking about metronidazole now, I'd like to ask the participants how much toxicity they're seeing. The VIN folks are going to turn off the moderation in a minute. This is a question for those of you with birthdays in July, August and September, please. How often do you see neurologic toxicity with metronidazole treatment of Giardia? ...a. never ...b. rarely, <5% of cases ...c. occasionally, 5-10% of cases ...d. 10-25% of cases ...e. > 25% of cases GA July, Aug, Sept folks, type fast GA GingerSanders: Responses
MichaelLeib: Thanks all - it seems like toxicity is rare, but can be devastating. Okay, while we're on the topic of treatment and have the moderation off, I have another question to ask. I'd like to know what you folks are usually doing regarding initial treatment. Let's make this a question for the January, February and March birthday people. Are you using: ...a. metronidazole ...b. fenbendazole ...c. something else (what?) Jan, Feb and Mar birthday folks, GA. GingerSanders: Responses
MichaelLeib: Thanks again, if the metronidazole is not working try fenbendazole KathyJames: Okay, I think we have one question we want to address from earlier because lots of people are asking: "which to trust if you see trophozoites/cysts but Elisa is negative...." RCAndrewThompson: if you cysts or trophozoites in faeces but the ELISA is negative then believe the microscopy results KathyJames: Specifically, what do we do with the patient with recurrent or chronic Giardia infection? GA MichaelLeib: First confirm the diagnosis. Send a fecal sample to a diagnostic laboratory or perform an ELISA test to make sure you are dealing with Giardia. Second, carefully evaluate client compliance. In some instances, hospitalization may be necessary to make sure the animal is receiving the medication. Next, check a fecal examination several days after finishing treatment. In many cases the fecal examination may be negative. If the diarrhea is continuing, look for another cause. If the diarrhea and a positive fecal examination occur at least 1 week after the negative fecal examination, consider reinfection. Perhaps the owner can restrict the animal's movement. In this instance, consider vaccination to prevent recurrence. If the fecal examination after treatment remains positive, use a different treatment. If the fecal examination still remains positive, consider a more complete GI workup to find an underlying primary problem. Consider vaccination, as preliminary anecdotal evidence suggests in some cases that vaccination may help the animal clear the parasite. Finally the animal may have a primary immunological deficiency, allowing chronic infection. GA _AskAQuestion: Do you think a lower does of Metronidazole would be effective and can't you reduce chance of toxicity by dividing dose BID? MichaelLeib: There is no evidence to suggest that splitting the dose BID is safer. Because of client compliance with metronidazole I suggest once a day treatment KathyJames: Mike, you mentioned vaccination. I'm sure folks have some questions on the vaccine. What are your thoughts on when we should use the Giardia vaccine? Mike, GA MichaelLeib: The Giardia vaccine for dogs and cats appears to be safe. It does not prevent infection, but does eliminate (dogs) diarrhea or reduce the number of affected cats with diarrhea. It also reduces the number of animals shedding cysts after infection, the number of cysts shed (dogs), and the number of days of shedding (dogs). I recommend vaccination in endemic areas. Also, the vaccination should be used in high-risk populations, such as military or police dogs, research facilities, foxhound kennels, breeding operations, etc. In addition, animals that become reinfected in nonendemic areas should be vaccinated. Finally, further evidence may suggest a role for vaccination in the chronically infected animal that cannot be cleared with treatment. GA KathyJames: Anne, can you talk about what kills Giardia cysts? GA AnneZajac: Giardia cysts are not difficult to kill. Most disinfectants will destroy canine Giardia cysts if several minutes contact time is allowed. In general, the quaternary ammonium compounds may seem to have the highest efficacy in dilutions normally used. Bleach is also effective. If at all possible, allow the cleaned area to dry thoroughly before allowing people or animals to return. GA _AskAQuestion: What about resistance to metronidazole? MichaelLeib: Studies in infected dogs have suggested that metronidazole is effective in only about 75% of dogs _AskAQuestion: is one vaccination considered enough protection, or is a series needed? MichaelLeib: The vaccine is labeled for 2 initial doses - so we need to follow these recommendations KathyJames: I know we all get this next question a lot. What kind of control program would you use in a kennel with a chronic Giardia problem? Anne GA AnneZajac: Giardia can be a real nuisance in a kennel or animal shelter situation where there is a high concentration of animals. The difficulty is that some carrier dogs will persistently contaminate the environment, even though they don't show any clinical signs that will allow you to recognize and treat them. You will have to evaluate each situation, but here are some things to consider:
_AskAQuestion: how young can the animal be to vax? MichaelLeib: Please check the label - I think its 8 weeks. _AskAQuestion: how efficient is fenbendazole in killing Giardia MichaelLeib: Fenbendazole has been 100% effective in experimental studies - however there have not been any studies in naturally infected pets KathyJames: Andrew, just to come full circle on the zoonotic aspects, can I/my children get Giardia from my dog or cat? GA RCAndrewThompson: Yes. Our laboratory and others have shown that dogs and cats can be infected with the zoonotic strains of Giardia. The converse is therefore true - our pets can catch it from us! GA KathyJames: With that, it's getting pretty late. Do we have any last minute questions from participants? If you're on the East Coast, feel free to slip out the back while we take one or two more questions. GA _AskAQuestion: lots questions about shampooing AnneZajac: It isn't like there has been real research on comparing shampoos--what we did in our study was use a standard shampoo and then use a mild disinfectant rinse followed by a water rinse. As I said though this really has been researched specifically this really has been researched specifically _AskAQuestion: How frequently do you treat all animals household, symptomatic or not? MichaelLeib: In Virginia, we treat all infected animals in the household. However in some endemic areas this may not be practical _AskAQuestion: Is there any other drugs that are effective besides these two mentioned? MichaelLeib: Febantal is also effective. It is converted to fenbendazole in the liver _AskAQuestion: How soon after treatment has begun can the infected animal remain zoonotic? RCAndrewThompson: from 48-72 hours KathyJames: I think we've gotten most of the question and we're out of time. Thanks everyone for coming. And please express your thanks to Fort Dodge for the generous sponsorship. Thank you for a good but unfortunately short session, _AskAQuestion: Night all -- sorry we could not get to all your great questions RCAndrewThompson: Goodnight everyone AnneZajac: good night and thanks for all your questions MichaelLeib: Thanks everyone - this was a lot of fun - even though I am not usually up this late!!! Goodnight all ***** Logging stopped: 4/7/2002 10:02:59 PM
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A Friendly Reminder: You are ultimately responsible for the care of your patients. Recommendations and discussions of cases should be considered as recommendations by colleagues for you to consider in your case management decisions. Dosages should be confirmed prior to dispensing medications.
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