Canine parovirus and feline panluekopenia: New ideas for prevention, risk assessment, and treatment (parts 1 & 2) (Proceedings)

Canine parvovirus (CPV) first made its unwelcome appearance in the late 1970s and since then has continued to evolve, with CPV 2a, 2b and 2c gradually replacing earlier strains. Feline parvovirus (FPV) has been around much longer and is one of the oldest known viral diseases in cats.  CPV is a variation of FPV and thus these viruses are remarkably closely related.  Unlike CPV, FPV only has one strain.  Cats can be infected with CPV and this virus has been recognized in healthy cats and cats with clinical signs. 

As an un-enveloped, double stranded DNA virus, parvoviruses are capable of persisting in the environment for months or even years. Unless vaccination is nearly ubiquitous in the surrounding community, periodic introduction into the shelter is inevitable. Because shedding can occur briefly in asymptomatic or pre-clinical animals, environmental contamination may go unrecognized. Disinfection, vaccination and housing practices must address this constant threat.

However, there is also some good news: although parvoviruses continue to evolve, they tend to be antigenically stable, and vaccination appears to confer reliable protection even against newer strains. In-house tests (e.g. IDEXX snap tests) are reasonably reliable and readily available, thus recognition of parvoviruses does not pose the diagnostic dilemma presented by some other conditions. The incubation period is well defined and relatively short (3-4 days in dogs and 5-7 in cats most common, but can be as long as 14), making quarantine of exposed animals a realistic possibility. Antibody titers can be used to assess risk in clinically healthy animals, allowing further refinement of quarantine decisions (see risk assessment below). Although parvovirus will always pose a risk for most shelters, the rate of infection can be greatly reduced by appropriate vaccination, quick recognition, appropriate segregation of diseased/exposed animals and vigilant cleaning and disinfection.

Who can be infected?

While puppies and kittens are most likely to suffer severe disease and death, any unvaccinated animal, of any age, especially if they have a co-infection, can become infected with parvoviruses. Some dog breeds have been reported to be more susceptible to this infection (e.g. “black and tan” breeds). However, these breed tendencies likely evolve and change over time as a result of natural selection against susceptible lineages, and no one breed should be assumed to be more or less susceptible than another (nor is there any indication for a differing vaccination schedule in a particular breed). The apparent frequency of CPV infection in some breeds or mixes in shelters (e.g., anecdotally, pit bulls) more likely reflects a lower frequency of vaccination and greater exposure rather than a true genetic risk.

Prevention

Vaccination is the cornerstone of parvovirus prevention in shelters and communities. In the absence of maternal antibody interference, a single modified live vaccine can confer protection within 3-5 days [1]. Research to date has found that currently available vaccines protect against all known strains of parvovirus, including parvovirus 2c [2, 3].

All dogs and cats > 4 weeks of age should be vaccinated at the time of shelter admission (or ideally, at least a week before), including those who are injured or mildly ill (in shelters where parvovirus is extremely rare, vaccination may be started at 6 weeks instead of 4 weeks). Revaccinate puppies and kittens every two weeks until 18-20 weeks of age [4] as long as they remain in the shelter and consider revaccinating adult dogs and cats at least once 2 weeks after the first vaccine or after adoption.

There is an intranasal FVRCP vaccine available for use in cats, however it must be noted that while the local immunity mounted from the herpes and calici viruses component of the vaccine is good after 2 vaccines, the parvovirus component is not.  Cats and kittens really do need a parenteral FVRCP to mount full immunity against FPV.

For pregnant animals, the risk of parvovirus infection must be balanced against the risk of vaccine-induced abortion. If the decision is made not to vaccinate a pregnant animal, titers should ideally be performed to evaluate susceptibility to infection (see below) and these animals must be carefully mechanically isolated unless confirmed to have an adequate titer. Because maternal antibody can interfere with vaccination in puppies and kittens under 20 weeks, they also need to be mechanically protected from exposure by ensuring that they are housed in easily cleaned and disinfected areas; handled and cared for by people with clean hands, shoes, and clothes; and ideally, removed from the shelter to foster care, adoption or rescue as quickly as possible.

Parvovirus enters and spread in shelters from dogs and cats infected in the surrounding community. A cost effective and humane strategy for long term control is to ensure that community members have ready access to affordable vaccines for their pets.

Animal flow through to minimize risk

In animal sheltering, many times we do not know the history of the animals in our care, including their vaccination history.  When this history is unknown, it must be assumed that animals entering the shelter are unvaccinated and thus have not developed immunity to parvovirus and other pathogens that we vaccinate for. 

One thing we do know is that time in a shelter is the greatest risk factor for being exposed to infectious disease and thus getting sick.  Having population management protocols that allow shelters to manage their intake and that allow animals to move through the shelter efficiently are crucial to limiting infectious disease spread in a shelter.  Detailed resources are available on www.aspcapro.org/stay a collaboration between the UC Davis Koret Shelter Medicine program and the ASPCA.

In addition to newly admitted animals, puppies and kittens (animals under 5 months) are another population that needs special consideration.  Depending on the shelter, puppies and kittens may have more physical protection if they are housed separate from adults or they may be more protected surrounded by healthy adults.         Regardless of what a shelter finds works best for them, separate PPE (long sleeved gowns or coveralls, shoe covers and gloves) needs to be designated to each litter and must be worn for cleaning, feeding and socializing animals. Unweaned puppies and kittens and puppies and kittens too young for adoption should be housed in foster homes until they are ready for adoption.  Shelters could also choose to adopt out the puppies from the foster home to avoid bringing the puppies and kittens back to the shelter.

Other factors to consider that reduce the risk due to environmental spread

• The facility is not crowded

• Dogs are housed singly or in stable pairs/groups

• Cats have compartmentalized housing (separate litterbox and sleeping areas)

• Dogs are not handled or removed  from their run during cleaning (i.e. double sided runs used correctly)

• Cats cages are spot cleaned

• Animal housing areas are steel, sealed concrete, or other non-porous, non-scratched surface and can be effectively cleaned and disinfected

• A proven parvocidal disinfect is used daily to disinfect all animal housing areas, including transport vehicles, exam surfaces and common rooms

• Separate tools and equipment are used for each area of the shelter

• Animals are handled  with hand washing or change of gloves between individuals

• Clinical signs appeared within a few days of shelter intake (and therefore the animal was more likely exposed in the community versus in the shelter)

Safe puppy socialization

It's easy to see the consequences when a puppy is exposed to CPV before vaccination has a chance to protect. This motivates us to carefully protect puppies from possible exposure to this deadly virus. However, the consequences of poor socialization are less immediately apparent, but may be equally severe. A puppy that has been isolated from other animals, people and a wide variety of experiences may grow up fearful or even aggressive. As we know in shelters, this may lead to fatal consequences if the dog is later surrendered due to these behaviors.

We need to balance the risk of CPV with the very real risk of poor socialization, and do our best to provide puppies with the best of both worlds: a variety of experiences in a relatively safe and clean environment.         

Disinfection

As noted above, parvovirus can remain viable for months to years, especially in a dark, moist environment [10]. There is no realistic way to “out-wait” parvovirus in a shelter setting: it must be mechanically removed or killed by one of the few effective disinfectants.

There is no benefit to a waiting period prior to re-use of a kennel or cage after parvovirus decontamination; either cleaning and disinfection was effective, or it was not. Waiting a day or even a couple of weeks will not result in a significant further decrease in contamination. To be on the safe side, kennels and cages should be completely cleaned, disinfected, and dried at least twice before re-use, however this can happen in a short period of time (e.g. 24 hours).

For areas such as yards and homes where disinfection is not an option, careful and repeated mechanical cleaning can be effective if applied diligently. Yards can be flushed with water and dried, and a disinfectant with reasonable efficacy in the face of organic matter (e.g. Accel or Trifectant) can be sprayed on the area using a pesticide applicator or hose-end sprayer. If cases of parvovirus occur after thorough efforts at cleaning, close the area to youngsters and unvaccinated animals for at least 6-12 months (and in general do not use grass or dirt areas for juvenile animals in a shelter). In the meantime, maximize exposure to sunlight and drying of the environment.

A couple of new products have come on the market in recent years that give us additional choices other than the old standby, bleach. Effective choices include 5% sodium hypochlorite (household bleach) at ½ cup per gallon (1:32 dilution) with a 10 minute contact time. Like all disinfectants, bleach must be used and stored correctly to be effective. In the case of bleach, this means application only to pre-cleaned surfaces free of organic matter. Bleach remains stable at least 200 days when undiluted, and at least a month after dilution provided it is stored in a light proof container [11, 12]. It is rapidly inactivated by light (within hours) and organic matter (immediately).

Products in the same family as bleach that have also been found effective include calcium hypochlorite (e.g. Wysiwash®) and sodium dichloroisocyanurate (e.g. Bruclean®). Like bleach, these have no detergent properties and must be applied to a pre-cleaned surface. Other proven products include potassium peroxymonosulfate [13] (e.g. Trifectant®) and accelerated hydrogen peroxide [14] (Accel®), which both reportedly have greater detergent properties and better activity in the face of organic matter compared to bleach and related products. Independent studies have repeatedly shown that quaternary ammonium disinfectants (e.g. Triple Two®, Rocal®) do not reliably kill  parvovirus and other un-enveloped viruses, in spite of repeated reformulation and label claims of efficacy [13, 15,16].

Recognition and diagnosis

A puppy or kitten with a bloody diarrhea may have an illness other than parvovirus, however all juvenile animals with bloody diarrhea in a shelter should be tested for parvovirus.  A positive test can be trusted and a negative test should be tested/treated for these other differentials.  However, a negative test does not completely rule out parvovirus and should still be isolated and retested if clinical signs do not resolve with treatment and time.

Diagnosis of canine parvovirus is fortunately reasonably straightforward in most cases. While not perfect, in-house fecal ELISA tests are reportedly quite specific and sensitive even for recently emerged strains. A recent study found that the IDEXX SNAP test detected 80%, 78% and 77% of parvovirus 2a, 2b, and 2c respectively [5]. 

Diagnosis of feline panleukopenia can also be done on an IDEXX brand Parvo snap tests.  False negatives may occur more commonly than when using these tests designed for canine parvovirus.  One small study found 20-50% false negatives and rare false positives (occurring 0-6% of tested samples) on various brands of tests [6].  Vaccine induced positives were rare on the IDEXX brand test (only 1/64 recently vaccinated kittens tested positive on an IDEXX brand test) while other brands had a higher rate of positive results following vaccination [7].

Other accessible in-shelter diagnostic tools include blood smear/CBC looking for leukopenia (<4-6 WBC per low power -10x- field or <1-3 WBC at high power -40x- field, often very dramatic) and, if an animal dies or is euthanized, in-house necropsy for characteristic segmental enteritis. 

Fecal samples can be submitted to a laboratory for PCR with rapid turn-around time; this method is sensitive to detect parvovirus infection but also more likely to detect vaccine virus in recently vaccinated animals. PCR analysis is the only method to distinguish between the various strains of parvovirus; however, this has minimal clinical relevance as the approach to prevention and treatment is identical regardless of strain.

Histopathology and immunohistochemistry on a necropsy specimen is the gold standard for diagnosis, and should be performed in atypical outbreaks if any animal dies or is euthanized (e.g. apparent infections in well-vaccinated animals; persistent outbreak in the face of good control measures).

As with any test, false results are possible. Negative results will occur later in the course of disease when virus is bound by antibody or no longer being shed. This should not be interpreted to contradict earlier positive results. Weak false positives may also reportedly occur due to recent vaccination. However, this is likely uncommon, particularly with the IDEXX brand SNAP test [8, 9].

In general, positive results in clinical animals should be taken seriously even in recently vaccinated dogs.

In general, testing should be reserved for animals with clinical signs or recently exposed/high risk animals. Because viral shedding can occur a few days before clinical signs appear, it can be helpful to test very high risk puppies and kittens even if they are showing no overt signs of infection, for instance unthrifty looking puppies from known high risk locations in a community. However, routine parvovirus testing in healthy appearing animals is costly, ineffective for controlling parvovirus in a shelter (as animals may test negative, then begin shedding hours or days later), and likely to result in an increased rate of false positive results (i.e. animals testing positive when they are not infected).

In all cases, history, signalment and clinical signs should be considered along with test results. With much at stake, confirmatory diagnostic testing should be performed, especially if the result does not fit the rest of the clinical picture.

Although diagnostic tests are quite effective to confirm or rule out parvovirus infection, this must go hand in hand with daily or more frequent monitoring of the population. If an unthrifty animal goes undetected for hours or days, the opportunity for spread is hugely magnified. Teach all staff and volunteers to be alert for dogs and cats with signs of illness and provide clear instructions for what to do should parvovirus be suspected. Train staff in correct use and interpretation of diagnostic tests and perform formal daily medical rounds during which the health of all animals in the shelter is evaluated.

Treatment

Treatment of parvovirus infected animals should only be undertaken in a shelter if sufficient facilities exist to isolate the patient such that the rest of the population is not put at risk and staff and veterinary oversight is adequate to ensure humane and appropriate care.

Other options include treatment at an off-site veterinary clinic or transfer to another shelter with sufficient facilities. Unless specifically set up for parvovirus treatment, foster and rescue homes are generally better used for quarantine of exposed animals rather than treatment of ill animals. If facilities or staff are insufficient and off-site options are not possible, euthanasia of infected animals may ultimately save lives by preventing continued spread.

Treatment is the same as that in a private practice setting, including anti-emetics, broad spectrum antibiotics to control secondary infections, fluid therapy and blood product transfusion as needed. Early enteral nutrition via syringe feeding or nasogastric tube is practical in some shelter environments and may be beneficial both in supporting the patient and decreasing the length of illness, resulting in decreased cost of care. A study in dogs infected with CPV recently completed at Colorado State University has shown that intensive at-home care at a fraction of the cost ($200-$300) had similar outcomes when compared to the inpatient “gold standard” of care ($1500-$3000).  The study should be published in 2014.

Treatments that are either not indicated or not available in the U.S. include hyperimmune serum, interferon omega, and Tamiflu [19]. Hyperimmune serum is not widely available (and serum from a dog that has simply been immunized is not equivalent), and this treatment likely has limited benefit by the time clinical signs have been recognized. Interferon omega has been shown to decrease mortality for CPV virus but the product is not available in the United States at this time. The mechanism of Tamiflu is specific to influenza viruses and there is neither evidence nor indication for its use in treatment of other infections.

Risk assessment (deciding how much to worry about exposed animals)

When one animal from a population is diagnosed with pavovirus, the question arises: what do you do about others in the environment? Are they all likely to get sick? Will widespread quarantine or depopulation be necessary? Or is it okay to simply carry on business as usual? Or should we be somewhere in between? The answers to these questions are dependent on several factors.

Not all exposed animals will become infected. Due to varying levels of maternal antibody, it is not even uncommon for only some members of a litter to develop disease.  The risk of infection depends on the animal's individual immune and vaccination status, the overall cleanliness of the environment and the level of proximity between the exposed and infected animal. The most important factor in disease risk is vaccination: a “fully” vaccinated animal over five months old is at very low risk of infection. However, even incompletely vaccinated animals may survive a possible exposure.

If a single case occurs in an area where all animals have been vaccinated and environmental spread risk is deemed low based on the above-listed factors, quarantine or depopulation may not be necessary. If spread is observed or few of the above precautions are in place, the whole ward or even the whole shelter may need to be considered at risk/exposed. An intermediate response is to assess risk for immediately adjacent kennels and cages only – this is logical only if exposure is likely much lower in dogs and cats elsewhere in the ward.

The key to managing an outbreak is accurately identifying which animals really need the additional investment of quarantine, rescue, or treatment, and which can be moved on through the system as usual with relative safety.

To determine which animals are protected by vaccination, the date of exposure needs to be determined. If the index case was sick at or very soon after intake, then that is the date of exposure. However, if the first case was in the shelter for some time before development of clinical signs, you will need to count backwards from the date of diagnosis to the earliest likely date of pre-clinical shedding. For example, dogs and cats can shed parvovirus for at least 3 days prior to development of clinical signs. We know that the vaccine generally provides protection within 3-5 days of administration (barring maternal antibody interference), so we combine these to estimate dogs and cats exposed to an index case in the shelter at least 8 days after vaccination are likely protected.

Titer testing is required to determine antibody status in juveniles (under the age at which maternal antibody interference with vaccination is possible) as well as adults with insufficient vaccine history.

Antibody levels can be determined via in house testing or a diagnostic laboratory. Titers correlate well with protection against parvovirus.  Titer testing can only be performed in clinically healthy animals. Clinically ill animals (of any age) should be SNAP tested if possible, treated if necessary, or quarantined if testing indicates they are not currently infected.

Exposed low risk animals can be moved on through the shelter as usual, e.g. to adoption (if rescue opportunities are limited these should be reserved for medium risk animals if willing; if rescue is unlimited, then rescue is a fine alternative to adoption for unexposed/low risk animals)

Performing a risk analysis to divide animals into the categories above can often render the number of animals requiring the more costly options of quarantine or treatment manageable. Even if some investment is made in diagnostic testing, costs can often be recovered in adoption fees for animals which would otherwise be euthanized.

Titers

Serology is a very useful tool to further clarify the need for quarantine of individual dogs [10, 11] and cats.  In-house serology tests can  be used and have the advantage of more rapid turn-around time as compared to sending out blood samples, often within minutes.  The feline test is not yet available in the US however, the canine test has been used successfully for evaluation in cats

The Synbiotics TiterCHEKTM kit is designed to test for canine distemper virus (CDV) or canine parvovirus (CPV) antibodies in canine serum.  The results are compared to positive and negative control wells and give non-quantitative positive or negative results.  This kit is a well test; each time the test is run two additional wells must be used to run a positive and negative control.  Because of this, the test is most economical when running several tests at once. Also since this is a well test rather than a “snap” kit, ensuring the staff running these tests is sufficiently skilled is essential. A how to use video can be found at http://www.youtube.com/watch?v=549GSe5xzR0

More recently, another in-house option has become available in the US, the VacciCheck ImmunoCombTM test by Biogal.  This kit provides semi-quantitative antibody titer levels for CPV and CDV (as well as Canine Adenovirus).  The kit is a "self-contained" dot ELISA titer test kit, not needing any reagent preparation.  The kit looks like a flat comb; each tooth of the comb is a test for an individual dog and includes the positive and negative controls.  Results can be scored by their shade relative to the positive on a scale from 1- 6.   Results develop for all three 3 viruses on the same comb simultaneously. The test provides results within approximately 20 minutes.  Our September 2011 Newsletter contains an article with more information on this test, and you can find a video demonstrating its use: http://www.youtube.com/watch?v=wQ4o6gFzqiw

Asymptomatic adult dogs and cats testing positive for protective titers are at low risk for developing infection. It is reasonable to move these dogs through the shelter as usual rather than placing them in quarantine.

Interpretation of titers in animals < 5 months of age is a little less clear-cut, as positive titers may reflect either an active immune response or waning maternal antibody. Puppies testing positive are likely low risk but this is less certain than with adults and immunity may rapidly wane. These puppies are relatively safe to move to adoption or rescue, but should leave the shelter quickly if possible and it is prudent to advise adopters or rescuers of their recent exposure to parvovirus. Continue their vaccine schedule as usual.

Puppies and kittens, especially heavily exposed animals or animals from high risk environments, should be snap tested before or in conjunction with titer testing to rule out early subclinical infection which could overcome maternally derived antibodies (MDA).  A positive snap test along with a positive titer, indicates subclinical infection and these animals should be isolated.  A negative snap and negative titer result would indicate that the puppy or kitten is not currently shedding but is not protected if exposed to the parvovirus and thus should be bathed and then quarantined.  A negative snap and positive titer result indicates that the puppy or kitten is not currently shedding and is likely protected (for now) if exposed to the parvovirus.  These puppies and kittens should be bathed and move out to adoption or rescue as promptly as possible.

All dogs and cats, of any age, testing negative for protective titers at the time of exposure must be considered high risk; however, many of these dogs will not develop infection. Quarantine for 2 weeks is indicated for this group if possible.

A caveat about risk

Remember that low risk and high risk are only that: evaluation or risk levels, not an absolute guarantee of a particular outcome. Virtually all tests have limitations, and the tests for antibody titers are no exception. Two studies estimated the sensitivity and specificity of the Synbiotics TiterCHEKTM at 92- 98% and 94-98% respectively. (20, 21) This means that occasionally dogs without protective titers will test positive and vice versa. For many shelters, the combination of evaluation of exposure level, clinical condition, titer and snap test results will lead to a reasonable degree of confidence of a dog's likelihood of infection, such that the risk for an adopter or rescuer in taking on a "low risk" dog would be no greater than adopting an untested dog at any other time (when the shelter was not experiencing an outbreak). However, if a truly no-risk scenario is desired, and it is affordable, quarantine of all exposed dogs for 14 days would be the safest bet. In many shelters, this is simply untenable, and evaluation of risk levels is the best way to manage a potential outbreak with minimal loss of life or spread of disease. Adopters and rescuers should be counseled accordingly.

Parvo simulator

Facing a parvovirus outbreak is scary and very stressful but when you have a moment to think about it, a thoughtful, lower stress process can get you through it.  We have created the PARVO OUTBREAK SIMULATOR that allows you to work through a real life outbreak scenario as many times as you like until you are confident in your risk assessment skills. The simulator only has dogs, however the same principles would apply for cats.

It also lets you get a sense for the fallibility of risk analysis – every once in a while, in the simulator as in life, you will do everything right and an infected animal will slip past your radar. However, you can also clearly see how many more lives are saved through careful risk assessment than either depopulation or failure to respond at all.

For a quick guide to risk analysis as a tool for outbreak management and some intriguing questions to help you get the most out of the parvo outbreak simulator experience, download the parvo outbreak simulator guide - http://www.sheltermedicine.com/documents/parvo-outbreak-simulator-guide  And for those of you who want to skip ahead to the answers or check your work, a sample set of answers to the simulator guide are also available at the website.

Quarantine

Quarantine is generally for 14 days.  However, if a shelter is transporting animals from a particular shelter and finds over time that all the cases break in a shorter time period, a shorter quarantine is acceptable. This can happen when exposure tends to happen early in the animal's stay at the source shelter (prior to transport), and by the time the animals are transported they have already had a few days to incubate illness if exposed. It can also happen when exposure is either heavy or not at all. In our experience, heavily exposed animals will usually break within 7 days of exposure.

Puppies and kittens should be bathed at the beginning of quarantine to prevent self-infection from virus remaining on fur as maternal antibodies wane.  All animals over 4 months of age should be vaccinated if they have not already or if under 5 months, the last vaccine was over 2 weeks prior. 

All adult animals should be housed singly if possible and if not, should be housed as cohorts; puppies and kittens can be housed in pairs and each kennel should have their own cleaning supplies. Have limited staff assigned to the quarantine ward and provide PPE (gloves, long sleeved gowns, shoe covers or separate shoes) that must be changed between puppies/pairs of puppies and after exiting the ward for adults. 

If possible bathe adult animals at the end of quarantine to remove lingering parvovirus remnants on fur, especially if exposure was heavy (bathe puppies and kittens too, if not done at the start of quarantine).

NOTE: Foot baths are not acceptable to control parvovirus – shoe covers or designated footwear to the isolation (sick animals) and quarantine (exposed animals) wards are necessary.

References

 Carmichael, L.E., J.C. Joubert, and R.V. Pollock, A modified live canine parvovirus vaccine. II. Immune response. Cornell Vet, 1983. 73(1): p. 13-29.

 Spibey, N., et al., Canine parvovirus type 2 vaccine protects against virulent challenge with type 2c virus. Vet Microbiol, 2008. 128(1-2): p. 48-55.

Larson, L.J. and R.D. Schultz, Do two current canine parvovirus type 2 and 2b vaccines provide protection against the new type 2c variant? Vet Ther, 2008. 9(2): p. 94-101.

Thompson, H., Efficacy of vaccination against canine parvovirus. Vet Rec., 2006. 159(17): p. 570-b-571.

Decaro, N., et al., Detection of canine parvovirus type 2c by a commercially available in-house rapid test. Vet J, 2009.

Neuerer et al, Comparison of different in-house test systems to detect parvovirus in faeces of cats.  Journal of Feline Medicine and Surgery, 2008. 10: p.247-251.

Patterson, E. V., M. J. Reese, et al. Effect of vaccination on parvovirus antigen testing in kittens.  J Am Vet Med Assoc, 2007.  230(3):p. 359-63.

Markovich, J. E., K. M. Stucker, et al. Effects of canine parvovirus strain variations on diagnostic test results and clinical management of enteritis in dogs. J Am Vet Med Assoc., 2012. 241(1): p. 66-72.

Decaro, N., C. Desario, et al. Detection of canine parvovirus type 2c by a commercially available in-house rapid test. Vet J.. 2009.

Larson, L., et al. Evaluation of a CPV-2 Fecal Parvovirus ELISA (SNAP Fecal Parvo Test (r)) from Idexx Laboratories."  Laurie Larson, Mariela Quesada, Eiman Mukhtar, K. Krygowska, and Ronald D. Schultz. in Conference for Research Workers in Animal Diseases. 2007. Chicago.

Patterson, E.V., et al., Effect of vaccination on parvovirus antigen testing in kittens. J Am Vet Med Assoc, 2007. 230(3): p. 359-63.

Larson, L.J., R.D. Schultz, and S. Newbury, Canine and feline vaccinations and immunology, in Infectious Disease Management in Animal Shelters, L. Miller and K.F. Hurley, Editors. 2009, Wiley-Blackwell: Ames, Iowa. p. 61-82.

Schultz, R.D., et al., Age and long-term protective immunity in dogs and cats. J Comp Pathol, 2010. 142 Suppl 1: p. S102-8.

Uttenthal, A., E. Lund, and M. Hansen, Mink enteritis parvovirus. Stability of virus kept under outdoor conditions. Apmis, 1999. 107(3): p. 353-8.

Rutala, W.A., et al., Stability and bactericidal activity of chlorine solutions. Infect Control Hosp Epidemiol, 1998. 19(5): p. 323-7.

Piskin, B. and M. Turkun, Stability of various sodium hypochlorite solutions. J Endod, 1995. 21(5): p. 253-5.

Eleraky, N.Z., L.N. Potgieter, and M.A. Kennedy, Virucidal efficacy of four new disinfectants. J Am Anim Hosp Assoc, 2002. 38(3): p. 231-4.

Omidbakhsh, N. and S.A. Sattar, Broad-spectrum microbicidal activity, toxicologic assessment, and materials compatibility of a new generation of accelerated hydrogen peroxide-based environmental surface disinfectant. Am J Infect Control, 2006. 34(5): p. 251-7.

Kennedy, M.A., et al., Virucidal efficacy of the newer quaternary ammonium compounds. Journal of the American Animal Hospital Association, 1995. 31(3): p. 254-8.

Scott, F.W., Virucidal disinfectants and feline viruses. Am J Vet Res, 1980. 41(3): p. 410-4.

Appel, L.D., Canine Parvo and Corona Virus, in Infectious Disease Management in Animal Shelters, L. Miller and K.F. Hurley, Editors. 2009, Wiley-Blackwell: Ames, Iowa. p. 197-209.

Litster A.L., Pressler B., Volpe A., Dubovi E., Accuracy of a point-of-care ELISA test kit for predicting the presence of protective canine parvovirus and canine distemper virus antibody concentrations in dogs.  Vet J. 2012 Aug. 193(2): p. 363-6.

Gray L.K., Crawford P.C., Levy J.K., Dubovi E.J., Comparison of two assays for detection of antibodies against canine parvovirus and canine distemper virus in dogs admitted to a Florida animal shelter.  J Am Vet Med Assoc, 2012. 240(9): p. 1084-1087.