SPECIAL REPORT

RAPPORT SPECIAL

Caring for pets of immunocompromised persons

Frederick J. Angulo, Carol A. Glaser, Dennis D. Juranek, Michael R. Lappin, Russell L. Regnery

Several million people in the United States havecompromised immune systems, including an esti-

mated 1 million people infected with human immuno-deficiency virus (HIV) (1). Immunocompromised per-sons are susceptible to a number of opportunisticinfections. However, although opportunistic infectionsmay be acquired from pets, and although 30 to 40% ofimmunocompromised persons may own pets (2), fewimmune-suppressed individuals are offered informa-tion about zoonoses prevention. In this report, we pro-vide veterinarians with guidelines for a zoonoses pre-vention program for their immunocompromised clients.

Conditions compromising the immune systemin human beingsThe immune system may become suppressed by under-lying diseases, treatments, or infectious diseases.Systemic diseases associated with immune suppres-sion in people include congenital immunodeficiencies,diabetes mellitus, chronic renal failure, alcoholism andliver cirrhosis, malnutrition, and certain types of cancers.Persons likely to receive immunosuppressive treat-ments are cancer patients, organ- or bone marrow-transplant recipients, and patients with autoimmunediseases. Other immunosuppressive treatments includesplenectomy and long-term hemodialysis. Althoughmany infectious diseases may cause immune suppression,the most profound suppression is caused by HIV.

Persons infected with HIV may be free of clinical signsor symptoms for many years. The acquired immuno-deficiency syndrome is a severe, life-threatening conditionthat represents the late clinical stage of HIV infection.

Can Vet J 1995; 36: 217-222

Reprinted, with permission of the American VeterinaryMedical Association, from J Am Vet Med Assoc 1994; 205:1711-1718. The report was based on a symposium held at the1993 AVMA Annual Meeting in Minneapolis, Minnesota.

Foodborne and Diarrheal Diseases Branch, Division ofBacterial and Mycotic Diseases (Angulo), Parasitic DiseasesBranch, Division of Parasitic Diseases (Juranek), and Viral andRickettsial Zoonoses Branch, Division of Viral and RickettsialDiseases (Regnery), National Center for Infectious Diseases,Centers for Disease Control and Prevention, Atlanta, Georgia30333, USA; the Center for AIDS Prevention Studies, PediatricInfectious Diseases, University of Califomia, San Francisco,California 94105, USA (Glaser); and the Department ofClinical Sciences, College of Veterinary Medicine andBiomedical Sciences, Colorado State University, Fort Collins,Colorado 80523, USA (Lappin).

The median time from HIV infection to development ofacquired immunodeficiency syndrome is approximately10 years, although some individuals have remainedasymptomatic 15 years after infection (3).

Severity of the immunologic damage in HIV-infectedpersons is usually monitored through measurement ofT-lymphocyte counts, especially absolute CD4 lym-phocyte counts (4). Trends in CD4 counts are com-monly used to make decisions regarding treatment,including prophylaxis against several opportunisticinfections, in HIV-infected individuals. The risk of devel-oping opportunistic infections increases as CD4 countsdecrease, especially when counts are <200 cells/51.When CD4 counts are >500 cells/SI, routine veterinarycare is probably adequate for companion animals ofHIV-infected clients. However, as CD4 counts decrease,implementing an expanded zoonoses prevention programbecomes increasingly important (5).

Public health role for veterinariansThrough monitoring the health of companion animals andeducating pet owners on zoonoses prevention, veteri-narians can help reduce the likelihood of an immuno-suppressed person acquiring certain zoonotic oppor-tunistic infections and can help their clients make moreinformed decisions about the risks and benefits of own-ing a pet (6,7). However, few veterinarians routinely dis-cuss ways to minimize transmission of zoonoses withtheir clients (8) and we believe even fewer inquireabout the general health of persons who live in thehousehold with the pet. Not surprisingly, althoughmany immunocompromised persons own pets, fewapparently receive information from veterinarians aboutpreventing transmission of opportunistic infectionsfrom their animals; in one survey (6), <I% of personsinfected with HIV had obtained such information froma veterinarian.

Despite receiving training about zoonoses, many vet-erinarians may be reluctant to discuss this topic, perhapsbecause they view educating people about zoonoses asa role for physicians. Our experience, however, is thatfew physicians provide immunocompromised personswith information about zoonoses and safe practices forpet ownership. In addition, when pets are thought to posea health risk, overly cautious recommendations areoften made, such as giving up pets altogether (9).

Although a high proportion of immunocompromisedpet owners have been advised to give up their pets, it isour experience that few part with their pets (10), sug-gesting a strong emotional attachment between many

Can Vet J Volume 36, April 1995 217

owners and their pets. Companion animals apparentlyprovide psychological benefits for some immunocom-promised persons, many of whom have feelings of iso-lation and rejection (11). A recent studya of HIV-infected persons revealed that pet ownership wasassociated with a decreased prevalence of depressivesymptoms, particularly in persons with less humansocial support.

In recent years, several nonprofit groups have orga-nized to help HIV-infected persons care for their pets.Over 3,000 HIV-infected clients currently receive ser-vices for their companion animals from such organiza-tions in the United States (Appendix). Several veterinar-ians have been active in these organizations, particularlywith the Education Committee of Pets Are WonderfulSupport (PAWS) in San Francisco, which has pub-lished several brochures for HIV-infected and otherimmunocompromised pet owners. These brochuresinclude Safe Pet Guidelines, Toxoplasmosis and YourCat, Zoonoses and Your Bird, and CatScratch Disease.

The veterinarian should be knowledgeableabout animal-associated opportunistic infectionsand be willing to educate immunocompromised

clients about zoonoses prevention.

Although we encourage all veterinarians to offer anexpanded zoonoses prevention program for theirimmunocompromised clients, we believe such a programrequires special commitment of the veterinarian. Theveterinarian should be knowledgeable about animal-associated opportunistic infections and be willing toeducate immunocompromised clients about zoonosesprevention. He or she should have access to a laboratorythat uses appropriate tests to detect the most commonopportunistic pathogens. The veterinarian also shouldrecognize that the increased financial costs of anexpanded zoonoses prevention program may be a hard-ship for some immunocompromised individuals.

Veterinarians should inform their clients of the exis-tence of an expanded zoonoses prevention program,while respecting the client's privacy (12). This may bestbe accomplished by announcing the program in a sign,brochure, or newsletter. If a client inquires about theprogram, the veterinarian then could ask, in the pri-vacy of the examination room, if someone in the house-hold has an immunosuppressive condition and if so,offer the program to the client.

Veterinarians should also educate their staff aboutconditions that cause immune suppression, includingHIV infection and acquired immunodeficiency syn-drome (13). The need for confidentiality should beemphasized. Because some people confuse feline andhuman immunodeficiency viruses, or mistakenly believeanimals can transmit HIV, the role of pets inHIV-associated disease and opportunistic infectionsshould be explained. Personnel should understand how

to use universal precautions when administering first aidto clients or staff (14).

GuidelinesAlthough the health risk of owning a companion animalis thought to be low for a person with an impairedimmune system, the risk can be further reduced withsimple precautions (15). If someone with a compro-mised immune system elects to own a companion animal,he or she should be more vigilant of the pet's health thanother pet owners are expected to be. Immunocompro-mised pet owners should be willing to seek veterinarycare early in the clinical course of illness in their pet.They also should recognize that an expanded zoonosesprevention program may be more expensive than routineveterinary care.Many of the opportunistic infections that infect

immunocompromised persons also infect animals, but theextent to which infected pets contribute to the trans-mission of these diseases to immunocompromised per-sons varies widely (15). The most common infectionsassociated with animals include Toxoplasma gondii,Cryptosporidium spp, Salmonella spp, Campylobacterspp, Giardia sp, Rhodococcus equi, Bartonella(Rochalimaea) spp, Mycobacterium marinum, andBordetella bronchiseptica. Each of these infections,except for possibly Bartonella spp, may be acquired fromsources other than pets (15). The proportion of theseinfections acquired from pets is not known, but isthought to be small (15). When considering their preva-lence and the proportion of cases originating from petsources, the most common infections acquired byimmunocompromised persons from pets apparently arethose caused by Salmonella and Campylobacter spp.

General recommendations - Immunosuppressedpet owners should be particularly careful about what theirpets eat and drink. We recommend they feed their petsonly high-quality commercial pet foods. If immuno-compromised persons insist on supplementing theirpets' diets, they should ensure that all egg, poultry,and meat products have been adequately cooked beforefeeding. Only pasteurized dairy products should beused. Tap water is adequate for most pets, unless it hasbeen shown to be unhealthy for human consumption, inwhich case commercial bottled water is preferred. Petsshould not be allowed to drink out of toilet bowls or haveaccess to garbage. They should be closely supervisedwhile outside, unless they are in their own fenced yard.Pets should not be allowed to scavenge, hunt, or eat otheranimals' feces. Immunocompromised persons shouldwash their hands after handling pets, especially beforeeating, and should avoid contact with their pet's feces.

Cats and dogs should receive routine annual veterinarycare, including a physical examination, standard immu-nizations, and a fecal examination for intestinal parasites.Pets owned by immunocompromised persons shouldreceive veterinary care early in the course of the pet's ill-ness. In animals with diarrhea, a fecal sample should beobtained for Salmonella and Campylobacter cultureand should be examined for Cryptosporidium andGiardia spp (screening for Cryptosporidium and Giardiaspp is not necessary for birds). Animals with diarrheashould not be allowed contact with immunocompro-mised persons.

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aAngulo FJ. Association of pet-ownership and prevention ofdepressive symptomology among HIV-infected persons (abstr),in Proceedings. Delta Soc 12th Annu Conf 1993; 19.

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Veterinarians should submit fecal samples to a clin-ical laboratory that performs the specific proceduresnecessary to detect these pathogens. Salmonella sppare isolated by culturing on standard selective media, thendetermining biochemical reactions. Selective mediaand appropriate incubation conditions, including amicroaerobic atmosphere, must be used to isolateCampylobacter spp (16). An acid-fast test may identifyCryptosporidium spp, but the indirect fluorescent anti-body test is more sensitive and specific (17,18). The pre-ferred concentration technique for detection of Giardiasp is the zinc sulfate method (19), but additional exam-inations may be required for diagnosis (20). Sampletransportation requirements, including transport mediaand preservatives, may differ among laboratories,emphasizing the need for advance coordination withthe laboratory.

If a Campylobacter sp is isolated from dogs or cats,treatment with erythromycin is recommended to elimi-nate shedding of organisms in feces (21). Fecal samplesfor Campylobacter culture should be obtained aftertreatment because shedding may recur in some animals(22). Treatment of pets with salmonellosis is usually notrecommended unless clinical signs of bacteremia are evi-dent, because treatment may prolong the usually transientshedding period (23). Pathogens should not be found onculture of fecal samples, collected at least 24 hoursapart when the pet is not receiving antibiotics, beforeintroducing or returning a pet infected with Salmonellaor Campylobacter spp to the home of a person withimpaired immune function. Giardiasis should be treatedwith metronidazole (24) or possibly albendazole, whichhas recently been shown to be an effective alternativetreatment for giardiasis in dogs (25). There is no effec-tive treatment for cryptorporidiosis, although sheddingin otherwise healthy pets is thought to be transient,often lasting <2 weeks (26,27).

Obtaining a pet- When obtaining a new pet, immuno-compromised persons should choose a healthy adultpet and avoid young animals, especially those withdiarrhea, since young animals with diarrhea are morelikely to be shedding Salmonella (23), Campylobacter(28), Cryptosporidium (29), or Giardia spp (30). Becausethe hygienic and sanitary conditions in facilities of petbreeders, pet stores, and animal shelters are highlyvariable, immunocompromised persons should exer-cise caution if obtaining a pet from these sources.Immediately after a pet is obtained, it should be

examined by a veterinarian. If the pet's health is ques-tionable, it should not be allowed contact with animmunosuppressed person. Examination of fecal samplesfrom healthy animals for pathogens may be advisable ifthe client's immune suppression is severe (eg, an HIV-infected client with a CD4 count below 200 cells/51).

Birds - Pet birds pose a low risk to immunocom-promised persons. A high proportion of HIV-infectedpersons have heard they should avoid owning petbirds (10), apparently because of concerns about infec-tions with Cryptococcus neoformans or M avium, butthese concerns are largely unwarranted. We do not rec-ommend screening healthy birds for C neoformans orM avium.

Cryptococcus neoformans does not cause diseasein birds because of their high body temperature.

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Cryptococcus neoformans is commonly isolated fromsoil and droppings of wild birds, especially pigeons, butseldom from droppings of pet birds (31). Transmissionto human beings is by inhalation of airborne organ-isms, but even in highly contaminated areas, only asmall number of organisms of the appropriate size toreach the alveoli are aerosolized (32). Pet birds aretherefore an unlikely source of Cryptococcus infectionfor human beings (15).

Pet birds are also an unlikely source of M aviuminfections in human beings because M avium isolatesfrom birds differ in antibiotic susceptibility, serovars, andgenetic sequencing from human isolates (33-35).Mycobacterium avium causes avian tuberculosis, anenteric granulomatous infection characterized by chronicweight loss and high WBC counts. Pet birds rarelydevelop avian tuberculosis, although the infection maybe more common in gray-cheeked parakeets and Amazonparrots (36). Diagnosis is by positive results on acid-faststaining of a direct fecal smear. Treatment of birdswith M avium infection may be possible with long-term antituberculous drugs (36). Although increasedrisk is not documented, persons with impaired immunefunction probably should not have contact with petbirds with clinical M avium infections.Immunocompromised persons should avoid contact

with bird droppings, although an increased incidence ofpsittacosis has not been reported among immuno-suppressed persons, and enteric pathogens, such asSalmonella and Campylobacter spp, apparently arerarely acquired from birds (15). To further reduce the riskof salmonellosis and campylobacteriosis, immuno-compromised persons should feed their birds only ahigh-quality diet, avoiding old seed that may becomecontaminated during storage. A reliable pet store may behelpful in selection of good-quality feed. Ideally, animmune-competent person should clean the cage, orthe immunocompromised person should wear glovesduring cleaning and immediately wash afterwards. Inill birds, samples of droppings should be obtained forculture of Salmonella and Campylobacter spp.Immunocompromised persons should avoid handling

wild birds because they are more likely than pet birds toshed Salmonella and Campylobacter spp (15). In addi-tion, because C neoformans is transmitted via inhalationand is commonly found in pigeon excreta, these personsshould avoid places where pigeon droppings areabundant.

Cats - Many immunocompromised persons havebeen told they should not own cats to avoid developingcerebral toxoplasmosis, a common opportunistic infec-tion among immunosuppressed persons (10). However,in 1 study of HIV-infected persons (37), an associationbetween cerebral toxoplasmosis and cat ownership wasnot found. Most cases of cerebral toxoplasmosis arecaused by reactivation of a previously latent infection,and not by an acute infection (38). In addition, most acuteinfections apparently are acquired through eating under-cooked meats (39). Nevertheless, immunosuppressedpersons should take precautions to prevent ingestionof infective oocysts from cat feces (37).

Cats are the definitive host of Toxoplasma gondii; theyare the only animals that pass oocysts in their feces. Onceoocysts are shed, they require 1 to 5 days to sporulate and

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become infective (40). Although shedding has beensuggested to be prolonged or recurrent in some cats(41), cats pass oocysts for only 2 to 3 weeks following pri-mary infection (40). Cats experimentally infected withfeline immunodeficiency virus and T gondii (42) orFeLV and Tgondii (43) did not have prolonged oocystshedding. Oocyst shedding also did not recur in adult catsfollowing repeated infections (44,45), administration ofclinical doses of glucocorticoids (46), or infection withfeline immunodeficiency virus (47).We do not recommend examination of feces for

Toxoplasma oocysts or testing of serum for Toxoplasmaantibodies in healthy cats. Fecal examination is sel-dom rewarding, because oocysts are shed only tran-siently and are so small they are easily missed. Currentserologic tests cannot accurately predict which cats areshedding oocysts. Most, but not all infected cats havecompleted oocyst shedding by the time antibodies aredetectable in their serum (40). Thus, a small proportionof seropositive cats may still be shedding oocysts. In con-trast, a seronegative cat may be uninfected or may berecently infected and currently shedding oocysts. Giventhe uncertainties in the interpretation of these laboratorytests and the relative ease in implementing measures toprevent zoonotic disease, these tests should not be usedto modify recommended precautions.

Preventing transmission of toxoplasmosis from catsshould focus on litter box hygiene (37). Litter boxesshould be cleaned daily and not placed in kitchen ordining areas. An immune-competent person shouldclean the litter boxes. If an immunocompromised personmust clean the litter box, he or she should wear glovesduring cleaning and immediately wash afterwards.Direct contact with cats is unlikely to result in trans-mission of toxoplasmosis because most cats do notleave feces on their fur for the 1 to 5 days required foroocyst sporulation.To prevent infection with T gondii, cats should not be

allowed to hunt and should not be fed raw or under-cooked meat. Because outdoor cats frequently defe-cate in gardens and T gondii oocysts may survive formonths under appropriate conditions (39), immuno-suppressed persons should wear gloves when gardeningor working with soil and should immediately washtheir hands afterwards.Although infrequently acquired from cats, salmo-

nellosis and campylobacteriosis may be the most com-mon infections acquired from cats in immunocompro-mised persons (15). The previously mentioned litterbox and feeding guidelines for preventing transmis-sion of toxoplasmosis also will help prevent transmissionof these enteric pathogens.

Bacillary angiomatosis is a newly recognized diseasesyndrome that has been diagnosed primarily amongimmunocompromised persons (48-53). Much remains tobe learned regarding the spectrum of human disease,prevalence of infection, and methods for prevention.Disease signs among immunocompromised persons arevariable and include undiagnosed febrile disease, seriousskin lesions, and life-threatening systemic disease.Although antibiotic treatment appears to be effective forimmunocompromised patients, such treatment mayneed to be prolonged (53,54).

Bacillary angiomatosis is caused by Bartonella (for-merly Rochalimaea) quintana or B henselae infections(54). Bartonella quintana infections have not been asso-ciated with cat contact, and a zoonotic reservoir forB quintana has not been described (54). In contrast,infections with B henselae, which is also the etiologicagent of cat scratch disease in immunocompetent persons,are associated with cat contact (55-59). Cat scratchdisease is diagnosed in an estimated 22,000 persons/yearin the United States (60); however, the prevalence ofB henselae infections among immunocompromised per-sons has not yet been determined.Domestic cats appear to be common reservoirs for

B henselae. Risk factors for humans acquiring B henselaeinfections include owning a cat (especially a kitten),being scratched by a cat, and having a cat with fleas(51,58,59). Bartonella henselae also has been isolatedfrom the blood samples of 41% of apparently healthycats, and from fleas from some of the same cats. How-ever, the potential role of fleas as effective vectors ofB henselae has not yet been established (56,61).Likewise, typically 40 to 50% of healthy cats haveevidence of past or current Bartonella infection, andantibody prevalence is higher among cats associatedwith infected human beings (59).Because the mechanisms of B henselae transmission

are not yet known, recommendations for preventionare limited to common-sense precautions (62). Kittensappear to pose a greater risk for disease than adult catsdo. Flea control may be beneficial in preventing trans-mission, but this has not been proven. Persons withimmune suppression should avoid activities that mayresult in cat scratches or bites. All cat scratches or bitesshould be washed immediately with soap and water.The effect of declawing of cats on the likelihood ofB henselae transmission is unknown. Similarly, theeffect of claw covers for reducing transmission has notbeen evaluated, but may be beneficial. Treating catswith antimicrobial agents has been suggested to clear theinfection, but further controlled studies are necessary(56); reinfection after the organism has been cleared hasnot been evaluated. Cats may have concurrent B henselaebacteremia and Bartonella-specific IgG antibodies, andthe relationship between antibody status and potentialinfectivity is still being investigated. For all these rea-sons, the value of Bartonella antibody testing in cats forindividuals making decisions regarding cat ownershipremains unclear, especially in environments where theprevalence of infection and rate of transmission in catsare high. Because early antimicrobial treatment is effec-tive in bacillary angiomatosis, all immunocompromisedpersons should inform their physician about the presenceof cats in the household.

Cats may develop cutaneous C neoformans infec-tions, but these are not considered public health hazardsbecause the organism is not aerosolized fromthese sites (63). Cats also may develop cutaneous ordisseminated M avium infections, but these organisms areubiquitous in the environment and human infectionshave not been associated with infected cats (64).Dogs - Bordetella bronchiseptica infections have

been reported in several immunocompromised persons(65), but routine use of the B bronchiseptica vaccine is

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not recommended except for dogs entering kennels or onshow circuits (66). In lieu of having their dogs vacci-nated, immunocompromised persons, especially thosewith advanced disease, should avoid exposing themselvesand their dogs to environments known to represent asource of B bronchiseptica (eg, boarding kennels, dogshows, or any situation in which dogs from severalsources are housed together).Although infrequently acquired from dogs, salmo-

nellosis and campylobacteriosis may be the most com-mon infections acquired from dogs in immunocompro-mised persons (15). Dogs are probably more likely thancats are to transmit these enteric infections to humanbeings, because rates of shedding of Salmonella,Campylobacter, Cryptosporidium, and Giardia organ-isms in feces are usually higher in dogs, and dogs aregenerally less fastidious about grooming themselves.

Other animals- Immunocompromised individualsshould not own reptiles because of the high rates ofcarriage and shedding of Salmonella organisms in rep-tiles (67). Persons who insist on keeping reptilian petsshould wear gloves when cleaning the cages and handlingthe pet, and should feed it a diet specifically processedfor reptiles (without raw meat or egg products).Treatment of reptiles for Salmonella infection is noteffective (67).

Small rodents, such as hamsters and gerbils, can alsotransmit Salmonella, Campylobacter, Cryptosporidium,and Giardia infections (68). Immunocompromised per-sons should be diligent about washing their hands afterhandling the animals or cleaning cages.A small number of Mycobacterium marinum infections

have been reported among HIV-infected persons (15). Allof these patients acquired their infection from contactwith pet fish usually when cleaning the aquarium (15).Gloves should be worn when cleaning an aquarium orwhen handling fish. Fish infected with M marinumshould be killed and the aquarium should be disin-fected before new fish are introduced (69).Immunocompromised persons should avoid contact

with young farm animals, especially animals withdiarrhea, because farm animals can act as a reservoir for

several infective agents, including Cryptosporidiumspp (15). Immunocompromised persons also shouldavoid exposure to swine, which are a known source ofB bronchiseptica (66). Although Rhodococcus equiinfection has been reported in several immunosuppressedpeople (70,71), most patients do not report a history ofrecently visiting farms or rural areas, and risk does notseem to be increased by having contact with adulthorses (15).References1. Centers for Disease Control. HIV prevalence estimates and AIDS

case projections for the United States. MMWR Morb MortalWkly Rep 1990; 39: 1-18.

2. Wise JK, Yang JJ. Veterinary service market for companion ani-mals, 1992. Part 1: Companion animal ownership and demo-graphics. J Am Vet Med Assoc 1992; 201: 990-992.

3. Brookmeyer R. Reconstruction and future trends of the AIDSepidemic in the United States. Science 1991; 253: 37-42.

4. Jewett JF, Hecht FM. Preventive health care for adults withHIV infection. JAMA 1993; 269: 1144-1153.

5. Filice GA, Pomeroy C. Preventing secondary infections amongHIV-positive persons. Public Health Rep 1991; 106: 503-517.

6. Spencer L. Study explores health risks and the human/animalbond. J Am Vet Med Assoc 1992; 201: 1669.

7. Gill DM, Stone DM. The veterinarian's role in the AIDS crisis.J Am Vet Med Assoc 1992; 201: 1683-1684.

8. Harvey JB, Roberts JM, Schantz PM. Survey of veterinarians'recommendations for treatment and control of intestinal para-sites in dogs: Public health implications. J Am Vet Med Assoc1991; 199: 702-707.

9. Burton BJ. Pets and PAWS; claims of health risks exaggerated.AIDS Patient Care 1989; 2: 34-37.

10. Bookseller T. Two new human-animal bond studies begin tobreak ground. DVM Magazine 1992; March: 18-31.

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12. Tannenbaum J. Medical-legal aspects of veterinary public healthin private practice. Semin Vet Med Surg 1991; 6: 175-185.

13. Tennyson AV. AVMA guidelines for dealing with AIDS infectedpersons in the veterinary workplace. J Am Vet Med Assoc 1989;195: 190-193.

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AppendixNonprofit organizations providing assistance to pet owners infected with

human immunodeficiencv virusCompanion Animal Support and Assistance Network (CASAN),810 Barret Ave, 266B, Louisville, KY 40204; (502) 574-5490.Hawaiian Humane Society: Pets Are Loving Support (PALS)Program, 2700 Waialae Ave, Honolulu, HI 96826; (808) 955-5122.Marin Humane Society: Share Program, 171 Bel Marin Keys Blvd,Novato, CA 94949; (415) 883-4621.Pet Pals, PO Box 190869, Dallas, TX 75219; (214) 521-5124.Pet Patrol, PO Box 980255, Houston, TX 77098; (713) 522-1954.PALS: 1438 Peachtree St, Atlanta, GA 30309; (404) 876-7257.PALS: Guerneville, P0 Box 1539, Guerneville, CA 95446;(707) 887-2729.Pets Are Wonderful Support (PAWS), 539 Castro St, San Francisco,CA 94114; (415) 241-1460.PAWS: Los Angeles, 7221 Santa Monica Blvd, Ste B,West Hollywood, CA 90046; (213) 876-7297PAWS: Chicago, 1153 N Dearborn 321, Chicago, IL 60610;(312) 465-3741.

PAWS: Orange County, 3111 Via Santo Tomas, San Juan Capistrano,CA 92675; (714) 489-2898.PAWS: Philadelphia, 1234 Locust, Philadelphia, PA 19107;(215) 985-0206.PAWS: St Louis, 3952 S Grand Ave, St Louis, MO 63118;(314) 865-0188.PAWS: San Diego, 1278 University Ave, San Diego, CA 92103;(619) 234-7297.PETS: Washington DC, 2001 0 St NW, Washington, DC 20009;(202) 234-7387.Pet Support Network, 1824 12th Ave, Seattle, WA 98122;(206) 322-5444.Pet Owners With AIDS/ARC Resource Service (POWARS),PO Box 1116, Madison Square Station, New York, NY 10159;(212) 744-0847.POWARS: Baltimore, PO Box 39364, Baltimore, MD 21212;(410) 783-8823.

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16. Blaser MJ, Berkowitz ID, LaForce FM, et al. Campylobacterenteritis: Clinical and epidemiologic features. Ann Intern Med 1979;91: 179-185.

17. McLauchlin J, Casemore DP, Harrison TG, et al. Identificationof Cryptosporidium oocyst by monoclonal antibody. Lancet 1987;1: 51.

18. Mtambo MM, Nash AS, Blewett DA, et al. Comparison of stain-ing and concentration techniques for detection of Cryptosporidiumoocysts in cat faecal specimens. Vet Parasitol 1992; 45: 49-57.

19. Barr SC, Bowman DD, Erb HN. Evaluation of two test proceduresfor diagnosis of giardiasis in dogs. Image Vet Res 1992; 53:2028-2031.

20. Isaac-Renton JL. Laboratory diagnosis of giardiasis. Clin Lab Med1991; 11:811-827.

21. Boosinger TR, Dillon AR. Campylobacterjejuni infections in dogsand the effect of erythromycin and tetracycline therapy on fecalshedding. J Am Anim Hosp Assoc 1992; 28: 33-38.

22. Monfort JD, Donahoe JP, Stills HF, et al. Efficacies of ery-thromycin and chloramphenicol in extinguishing fecal shed-ding of Campylobacter jejuni in dogs. J Am Vet Med Assoc1990; 196: 1069-1072.

23. Fox JG. Campylobacter infections and salmonellosis. Semin VetMed Surg 1991; 6: 212-218.

24. Kirkpatrick CE. Feline giardiasis: A review. Small Anim Pract1986; 27: 69-80.

25. Barr SC, Bowman DD, Heller RL, et al. Efficacy of albendazoleagainst giardiasis in dogs. Image Vet Res 1993; 54: 926-928.

26. Wilson RB, Holscher MA, Lyles SJ. Cryptorporidiosis in a pup.J Am Vet Med Assoc 1983; 183: 1005-1006.

27. Seasick DB, Gosser HS, Styer EL. Intestinal cryptospori diosis intwo pups. J Am Vet Med Assoc 1984; 184: 835-836.

28. Altekruse SF, Hunt JM, Tollefson LK, et al. Food and animalsources of human Campylobacter jejuni infection. J Am VetMed Assoc 1994; 204: 57-61.

29. Mtambo MM, Nash AS, Blewett DA, et al. Cryptosporidiuminfection in cats: Prevalence of infection in domestic and feral catsin the Glasgow area. Vet Rec 1991; 129: 502-504.

30. Stykes TJ, Fox MT. Patterns of infection with Giardia in dogs inLondon. Trans R Soc Trop Med Hyg 1989; 83: 239-240.

31. Levitz SM. The ecology of Cryptococcus neoformans and the epi-demiology of cryptococcosis. Rev Infect Dis 1991; 13: 1163-1169.

32. Powel KE, Dahl BA, Weeks RJ, et al. Airborne Cryptococcus neo-formans: Particles from pigeon excreta compatible with alveolardeposition. J Infect Dis 1972; 125: 412-415.

33. Denner JC, Tsang AY, Chatterjee D, et al. Comprehensiveapproach to identification of serovars of Mycobacterium aviumcomplex. J Clin Microbiol 1992; 30: 473-478.

34. Byrne SK, Geddes GL, Isaac-Renton JL, et al. Comparison of invitro antimicrobial susceptibilities of Mycobacterium avium-M.intracellulare strains from patients with acquired immunodeficiencysyndrome (AIDS), patients without AIDS, and animal sources.Antimicrob Agents Chemother 1990; 34: 1390-1392.

35. Tsang AY, Denner JC, Brennan PJ, et al. Clinical and epidemio-logical importance of typing of Mycobacterium avium complex iso-lates. J Clin Microbiol 1992; 30: 479-484.

36. Rosskopt WJ, Woerpel RW. Successful treatment of tuberculosisin pet psittacines, in Proceedings. Assoc Avian Vet 1991; 238-251.

37. Wallace MR, Rossetti RJ, Olsen PE. Cats and toxoplasmosisrisk in HIV-infected adults. JAMA 1993; 269: 76-77.

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