FELINE CORONAVIRUS, FIP, AND THE GASTROINTESTINAL TRACT DIANE ADDIE Feline coronavirus can cause gastrointestinal signs in different ways Gastrointestinal tract related clinical signs due to FCoV manifests in 4 main ways: 1. during primary infection: as small intestinal diarrhoea ± vomiting 2. persistently infected (FCoV carrier) cats can present with large intestinal diarrhoea 3. colonic form of non-effusive FIP causing thickening and lesions 4. as enlarged mesenteric lymph nodes FCoV transmission is mainly indirect: from contaminated litter trays To see a film of FCoV transmission: In English http://www.youtube.com/watch?v=rkqujeqneqs In French http://www.youtube.com/watch?v=jrnopbfar8a&feature=plcp In German http://www.youtube.com/watch?v=qpwl3e_2wfw FCoV transmission is faecal-oral, not direct or transplacental. The majority of FCoV infection goes undetected: cats becomes infected, shed FCoV in the faeces from around 2 days post-infection, seroconvert around 3 weeks post-infection, shed virus for on average 2-3 months, stop shedding virus, then gradually become antibody negative. Recovered cats are then susceptible to re-infection by the same, or another, FCoV strain: immunity is very short-lived (likely IgA and cell-mediated immunity in the gut). Contrary to the results of experimental laboratory infections of cats, cats naturally infected in the field are most likely to develop FIP on their first encounter with the virus, rather than subsequent infections (so called antibody disease enhancement (ADE) is a laboratory artefact: this is an important fact in the Felocell FIP vaccine argument: Felocell FIP does NOT induce ADE).
Diarrhoea, and occasionally vomiting, in primary feline coronavirus infection Diarrhoea, and occasionally vomiting, occurs in kittens and some adult cats at primary FCoV infection, the diarrhoea is small intestinal and usually self-limiting within a few weeks. However, occasionally the virus can be responsible for a severe acute or chronic course of vomiting or diarrhoea with weight loss, which may be unresponsive to treatment, continue for months and even result in death. Kipar et al, 1998 However, there are many other causes of diarrhoea in cats which require to be excluded before a diagnosis of FCoV diarrhoea can be made. Feline coronavirus as a cause of postweaning kitten diarrhoea with or without stunting In situations where FCoV is endemic, kittens will become infected as soon as maternally derived antibody (MDA) wanes. This phenomenon is commonly observed in breeding catteries as diarrhoea in 5-7 week old kittens. Sometimes the nictitating membranes also protrude. The kittens may or may not experience mild upper respiratory signs at the same time. Another significant clinical sign, pointing to FCoV as the cause of the diarrhoea, is that littermates tend to be of uneven sizes Addie & Jarrett, 1992 though this may not become apparent until the kittens are slightly older. However, there are many other causes of diarrhoea in cats which require to be considered before a diagnosis of FCoV diarrhoea can be made (for example Tritrichomonas foetus which tends to affect the same group of cats young cats living in crowded multicat environments) or torovirus, which can also cause diarrhoea with protruding nictitating membranes. Muir et al, 1990 FCoV infection as a cause of chronic diarrhoea in the carrier cat Persistently infected FCoV carrier cats usually appear to remain in adequate health, though some develop chronic large intestinal diarrhoea and faecal incontinence in older age. Again, there are many causes of chronic diarrhoea in the older cat, and FCoV carrier should be near the bottom of any list of differential diagnoses: it is uncommon. Detection of carrier cats requires positive faecal reverse transcriptasepolymerase chain reaction (RT-PCR) test results for nine months. FCoV carrier cats rarely develop FIP. Remarkably, the level of virus shedding remains incredibly constant: giving virtually identical Ct (cycle threshold) results month after month (though viral quantity decreases slightly as the cat ages).
Intestinal / Colonic FIP Colonic FIP is a form of non-effusive FIP that usually presents as either diarrhoea, or, sometimes, as constipation, in addition to the usual clinical signs of non-effusive FIP: i.e. chronic weight loss, chronic mild pyrexia and anorexia. Lesions are most commonly found in the colon or ileo-caecocolic junction but may also be in the small intestine. Cats may have various clinical signs as a result of this lesion - usually constipation, chronic diarrhoea, or vomiting. Palpation of the abdomen often reveals a thickened intestine and raised mesenteric lymph nodes. A hematologic finding may be increased numbers of Heinz bodies, in addition to the lymphopenia and non-regenerative anaemia customary in FIP. Biochemical findings tend to be hyperglobulinaemia, raised bilirubin levels and raise alpha 1 acid glycoprotein (AGP). Feline infectious peritonitis of the mesenteric lymph node FIP presenting as an enlarged mesenteric lymph node, with few other clinical signs other than weight loss, malaise and fever, has been reported in the cat Kipar et al, 1999 and is the form of FIP most commonly seen in the ferret. The major differential diagnoses are neoplasia, toxoplasmosis, and other pyogranuloma inducing infections.
Diagnosis In this section, only the diagnosis of FCoV-related gastrointestinal signs will be addressed, since FIP diagnosis has been covered in the FIP diagnosis webinar notes. The most recent FIP/FCoV diagnosis algorithms can always be found on the www.catvirus.com website. Primary feline coronavirus infection in adult and kitten gastrointestinal signs No specific tests exist for coronaviral enteritis, and FCoV can only be assumed to be the cause of gastrointestinal clinical signs in FCoV-seropositive or RT-PCR fecal-positive cats in which all other possible causes have been carefully eliminated. Even biopsy is of limited use because the histopathologic features of villous tip ulceration, stunting, and fusion, or pyogranulomatous inflammation, are nonspecific. FCoV infection may only be confirmed if immunohistochemical (IHC) or immunofluorescent staining of gut biopsies is available (recommended laboratory for IHC in the UK is Liverpool Vet School. If using another laboratory ask whether they will perform a non-fcov antibody control on every section of tissue cat tissue is very sticky, leading to false positive results if the laboratory has not performed adequate controls.). Exclusion of FCoV as a cause of GI signs is easier than diagnosing FCoV as the cause. Although serologic testing has limitations, it is clear that seronegative cats - as determined by a reliably sensitive * FCoV antibody test - do not have clinical signs related to FCoV infection. The only exception to this will be in initial FCoV infection, before the kitten or cat has had time to seroconvert (antibodies generally appear 18 21 days post infection) and in this case, an RT-PCR on faeces will be useful a negative result will exclude FCoV definitively (provided the test is sensitive enough), but a positive result will simply indicate that FCoV is one of many possible causes of the GI signs
other parasitic, protozoal, dietary, bacterial and viral causes will require to be excluded, as well as conditions such as intusussception, foreign body (commonly trichobezoar), inflammatory bowel disease, tumour, etc. etc. *A comparison of FCoV antibody tests was published by Addie et al (2015) and can also be found on catvirus.com. Key message: a negative FCoV antibody test rules out FCoV as a cause of diarrhoea in kittens and cats over 10 weeks of age However, a positive antibody test only indicates that FCoV is a possible diagnosis: other possible causes MUST be excluded before making a diagnosis of FCoV Persistent FCoV infection as a cause of chronic diarrhea Detection of carrier cats requires positive faecal reverse transcriptase-polymerase chain reaction (RT-PCR) test results once a month for nine months. A single negative FCoV antibody test rules out FCoV as a diagnosis. Other causes (e.g. hyperthyroidism, inflammatory bowel disease, intestinal lymphoma or other neoplasia, pancreatitis, intestinal parasites, protozoa, etc) need to be investigated fully and eliminated before a diagnosis of FCoV diarrhoea can be arrived at. Intestinal / Colonic FIP Definitive diagnosis of intestinal FIP is by immunohistochemistry of a full thickness biopsy of the intestine. RT-PCR of faeces to detect FCoV will likely be positive, but since it is also positive in so many cats who do not have FIP, a positive result is of limited value. However a negative faecal FCoV RT-PCR, or RT-PCR on a FNA of the lesion, would be likely to rule out colonic FIP as would a negative FCoV antibody test. In addition, cats with intestinal FIP would be expected to have elevated AGP levels; lymphopenia; hypergammaglobulinaemia and a non-regenerative anaemia with Heinz bodies.
Feline infectious peritonitis of the mesenteric lymph node Viral detection on a fine needle aspirate (FNA) from enlarged mesenteric lymph nodes is a very useful method of diagnosing FIP, since histopathology of an enlarged lymph node is often vague, only describing pyogranulomatous inflammation. Quantitative (real time or Taqman) RT-PCR tests can give an idea of the amount of virus present, which will be high in cats with mesenteric lymph node FIP. FCoV RT-PCR and can be performed at the University of Glasgow Veterinary Diagnostic Services laboratory: send the FNA in 0.25ml of saline in a plain tube. Treatment Updates on FIP/FCoV treatment can always be found on the www.catvirus.com website. Coronavirus enteritis in initial infection in kittens, adults and carrier cats Treatment is symptomatic and supportive: use of fluid-electrolyte replacement and restricted caloric oral diet with living natural yogurt or with probiotics (e.g. Protexin, International Animal Health Products (IAHP), Australia and New Zealand) may be useful. Any cat with diarrhoea should receive weekly vitamin B12 injections. Applaws (MPM products, Cheshire) and Almo Nature chicken and pumpkin tinned cat foods are remarkably useful in controlling diarrhoea. Addie personal observation Some persistently infected carrier cats with diarrhoea respond to low doses of prednisolone (0.5 to 1 mg/day per cat) but remember that you MUST have established that they really are a carrier cat, otherwise immunosuppressing a non-carrier FCoV infected cat could result in FIP. No specific antiviral treatment has yet been demonstrated to cure FCoV diarrhea although interferon omega (Virbagen Omega, Virbac, France) has been shown to reduce FCoV shedding.gil et al, 2013 Gil et al (2013) gave 1 million units/kg recombinant feline interferon omega subcutaneously for 5 daily injections beginning at day 0, 14, and 60 to 16 shelter cats co-infected with FCoV and FeLV or FIV. Two cats didn t shed FCoV at all, thus the FCoV group was actually 14 cats: FCoV shedding appeared to reduce but not statistically significantly and unfortunately there was no control group, nor was it determined whether it was type I or type II FCoV in the shelter (type II FCoV is only shed for a couple of weeks; though the shelter virus was probably type I). Overall clinical scores improved and 13 cats shedding feline calicivirus stopped shedding virus. Diarrhoea was only noted in two cats, mostly the faeces of the FCoV infected cats were reported as normal.
Presumably when / if the 3C-like protease inhibitor described by Kim et al (2016) becomes commercially available it will be the treatment of choice for FCoV-associated diarrhoea. Colonic and mesenteric lymph node FIP Since FIP is immune mediated, treatment aims at diminishing the immune reaction, usually using quite high doses of prednisolone, as a sliding dose (i.e. 2mg/kg/day for 10-14 days, reducing to 1 mg/kg/day for 10-14 days, then 0.5 mg/kg/day... and so on). Until recently, FIP was incurable and most so-called recovered cats were probably simply misdiagnosed. However, recombinant feline interferon omega (refifnω) (Virbagen Omega, Virbac, France) has been introduced which, according to one paper effected a cure in around 25% of cats and remission in others, but in another controlled study no benefits were found. Nevertheless, in these cases, this author believes that refifnω given at doses of 100,000 units per day per os will give remission to some of these cats. To obtain this dose, reconstitute a 10 million unit vial, withdraw ten 0.1ml aliquots and freeze 9 of them (Virbagen Omega can last for months in the freezer). Put the remaining 0.1ml into 4.9 mls of water and give 0.5 ml to the cat per day. Store the diluted refifnω in the fridge, where it will last for 3 weeks. Human interferon is not recommended because interferon is fairly species specific and cats develop antibodies to human interferon after 6 weeks, although if that is all that is available to you, then it is better than nothing. Human interferon can be given orally to cats. Polyprenyl Immunostimulant (Sass & Sass, Inc, Oak Ridge, TN 37830, USA) is a mixture of phosphorylated, linear isoprenols which upregulates biosynthesis of Th-1 cytokine mrnas. It was used successfully in three cats with non-effusive FIP, with survival times of 14 months, over 26 and 27 months, but had no beneficial effect on cats with effusive FIP. Legendre & Bartges, 2009 However, Legendre presented at AAHA that 22% of 58 cats with FIP were alive at 6 months, and only 5% at one year. The dose of 3mg/kg orally is given three times a week until cure or death. The effect of PPI on FCoV associated diarrhoea, or FCoV shedding, has never been reported. For the latest on PPI availability in Europe and further information on FIP treatment visit the FIP treatment page of my catvirus website. One needs permission from the VMD to import it into the UK and it can be purchased from the Vetimmune website. PPI should not be given with steroids.
Nutrition Many of the larger cat food companies uses poor quality, cereal based, protein in their foods. Excessive amounts of omega 6 polyunsaturated fatty acids, such as are found in cereal based diets, promote chronic inflammation. In this author s opinion, feeding as varied and natural a diet as possible to cats with FCoV infection and FIP is essential, avoiding highly processed commercial foods. The aim should be to source a high protein food with adequate levels of omega 3 oils, especially eicosapentaenoic acid (EPA): EPA supplementation has been shown to reduce monocyte adhesiveness to blood vessel walls. EPA is found in salmon, amongst other things. Fish oil, rich in omega 3 fatty acids, may be helpful in treating humans with ulcerative colitis and could help cats with FCoV infection, though one has to be wary that in cats too much vitamin A will cause excessive bone to be laid down in joints, so this avenue of treatment must only be pursued with caution. Unlike humans, cats are unable to synthesize arginine: it is an essential amino acid in the cat. Arginine deficiency impairs the capacity of T cells to proliferate and to produce interferon gamma. Arginine is found naturally in meat. The author is aware of two commercially available cat foods in Europe which contain high quality ingredients and are not full of additives: Applaws (MPM products, Cheshire, UK www.mpmproducts.co.uk) and Almo Nature (Italy, www.almonature.com) no doubt there are others. In this author s experience, a natural tinned food containing chicken and pumpkin (Applaws, MPM products, UK) stops diarrhoea in some cats without need for further medication. In addition, these natural foods are highly palatable, reducing or eliminating the need to use appetite stimulants.
Appeal for samples We are looking for fine needle aspirates (FNA) of mesenteric lymph nodes from FCoV antibody or RT-PCR positive cats without FIP (i.e. healthy or suffering from a non-fip disease). Please send the FNA in 0.25ml saline in a plain tube, plus a blood sample (or the FCoV antibody result) by first class post (no need for ice) to: FAO Dawn Dunbar Veterinary Diagnostic Services Bearsden Rd Glasgow G61 1QH UK Please put in a cover letter or sample submission form requesting FCoV RT-PCR on the FNA and FCoV antibodies tested on the blood sample. Please contact me at draddie@catvirus.com so that I can tell you how the tests can be done for free. Work with me on a FCoV elimination project If you have a FCoV infected household with an owner who is keen to eliminate FCoV and who would be interested in participating in a research study, please contact me at draddie@catvirus.com to discuss participation. I am a veterinary surgeon: everything you tell me about your patients will be kept absolutely confidential. Acknowledgements Diane is deeply grateful to all the veterinary surgeons and guardians who have supplied samples from naturally infected cats for almost three decades, helping her to avoid laboratory experiments on cats. No conflicts of interest Diane holds no shares or directorships in any of the products mentioned. However, if you use the Zooplus link on her catvirus website to buy pet supplies, not only will you receive a discount, but she will receive an affiliate fee and she profits from sales of her book FIP and Coronavirus available as e-books from her website and in print from Amazon in English and Spanish.
References, further reading and useful websites Diane Addie s FCoV and FIP website: www.catvirus.com Jody Gookin s website on Tritrichomonas foetus: www.cvm.ncsu.edu/docs/personnel/gookin_jody.html Applaws food: www.applaws.co.uk To source Applaws or Almo Nature in Europe: www.zooplus.com To obtain Protexin probiotic: www.pets-megastore.com.au/protexinprobioticpowder250gms-p-1733.html Addie DD, Jarrett O. 1992 A study of naturally occurring feline coronavirus infection in kittens. Vet. Rec. 130 133-137 Addie, DD. Feline coronavirus. 2012 Infectious Diseases of the Dog and Cat. 4th edition. Editor: Greene, Craig. Published by W.B. Saunders Elsevier Company, 11830 Westline Industrial Drive, St. Louis, Missouri 63146, USA. ISBN 978-1-4160-6130-4 92-108 Addie DD, McDonald M, Audhuy S, Burr P, Hollins J, Kovacic R, Lutz H, Luxton Z, Mazar S, Meli ML. 2012 Quarantine protects Falkland Islands (Malvinas) cats from feline coronavirus infection. J Feline Med Surg. 14(2):171-6. Addie DD, le Poder S, Burr P, Decaro N, Graham E, Hofmann-Lehmann R, Jarrett O, McDonald M, Meli ML. 2015 Utility of feline coronavirus antibody tests J Feline Med Surg 17(2):152-62 Bell ET, Gowan RA, Lingard AE, McCoy RJ, Slapeta J, Malik R. 2010 Naturally occurring Tritrichomonas foetus infections in Australian cats: 38 cases. J Feline Med Surg. 2010 Dec;12(12):889-98. Cohen TM, Blois S, Vince AR. 2016 Fatal extraintestinal toxoplasmosis in a young male cat with enlarged mesenteric lymph nodes. Can Vet J 57, 5: 483-486 Gil S, Leal RO, Duarte A, McGahie D, Sepúlveda N, Siborro I, Cravo J, Cartaxeiro C, Tavares LM. 2013 Relevance of feline interferon omega for clinical improvement and reduction of concurrent viral excretion in retrovirus infected cats from a rescue shelter. Res Vet Sci. 94(3):753-63
Gookin JL, Stebbins ME, Hunt E, Burlone K, Fulton M, Hochel R, Talaat M, Poore M, Levy MG. 2004 Prevalence of and risk factors for feline Tritrichomonas foetus and giardia infection. J Clin Microbiol. 42(6):2707-10. Gruffydd-Jones TJ. 2009. Current thoughts on feline inflammatory bowel disease. www.vin.com/proceedings/proceedings.plx?cid=wsava2009&category=8064&pid=53593&o=generic Harvey CJ, Lopez JW, Hendrick JM. 1996 An uncommon intestinal manifestation of feline infectious peritonitis: 26 cases (1986-1993). JAVMA 209 6 1117-1120 Haubert NJ, Padovan GJ, Zucoloto S, Vannucchi H, Marchini JS. 2010 Experimental induction of steatosis in different tissues after the ingestion of a carbohydrate-rich diet: effect on the liver, on the heart and on indicators of oxidation. Arq Gastroenterol. 47(4):388-92. Hodgkins EM 2007 Your Cat: A Revolutionary Approach to Feline Health and Happiness Thomas Dunne Books, US ISBN-10: 0312358016 ISBN-13: 978-0312358013 Legendre AM, Bartges JW. 2009 Effect of Polyprenyl Immunostimulant on the survival times of three cats with the dry form of feline infectious peritonitis. J Feline Med Surg. 11 624-626 Lingard AE, Briscoe K, Beatty JA, Moore AS, Crowley AM, Krockenberger M, Churcher RK, Canfield PJ, Barrs VR. 2009 Low-grade alimentary lymphoma: clinicopathological findings and response to treatment in 17 cases. J Feline Med Surg. 2009 Aug;11(8):692-700. Epub 2009 Jul 2. Kidder AC, Johannes C, O'Brien DP, Harkin KR, Schermerhorn T. 2008 Feline dysautonomia in the Midwestern United States: a retrospective study of nine cases. J Feline Med Surg. 10(2):130-6. Kim Y, Liu H, Galasiti Kankanamalage AC, Weerasekara S, Hua DH, Groutas WC, Chang K-O, Pedersen NC. (2016) Reversal of the Progression of Fatal Coronavirus Infection in Cats by a Broad-Spectrum Coronavirus Protease Inhibitor. PLoS Pathog 12(3): e1005531. doi:10.1371/journal.ppat.1005531. pmid:27027316 Kipar A., Kremendahl J., Addie D.D., Leukert W., Grant C. K. Reinacher M.. 1998 Fatal enteritis associated with coronavirus infection in cats. J. Comp. Path. 119: 1-14 Kipar A, Koehler K, Bellmann S., Reinacher M. 1999 Feline infectious peritonitis presenting as a tumour in the abdominal cavity. Veterinary Record 144 118-122
Maggs DJ, Sykes JE, Clarke HE, Yoo SH, Kass PH, Lappin MR, Rogers QR, Waldron MK, Fascetti AJ. 2007 Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease. J Feline Med Surg. 9(2):97-108. Muir P, Harbour DA, Gruffydd-Jones TJ, Howard PE, Hopper CD, Gruffydd-Jones EA, Broadhead HM, Clarke CM, Jones ME. 1990 A clinical and microbiological study of cats with protruding nictitating membranes and diarrhoea: isolation of a novel virus. Vet Rec. 127(13):324-30. Modolell M, Choi BS, Ryan RO, Hancock M, Titus RG, Abebe T, Hailu A, Müller I, Rogers ME, Bangham CR, Munder M, Kropf P. 2009 Local suppression of T cell responses by arginase-induced L-arginine depletion in nonhealing leishmaniasis. PLoS Negl Trop Dis. 3(7):e480. Munder M. 2009 Arginase: an emerging key player in the mammalian immune system. Br J Pharmacol. 158(3):638-51. Novellas R, Simpson KE, Gunn-Moore DA, Hammond GJ. 2010 Imaging findings in 11 cats with feline dysautonomia. J Feline Med Surg. 12(8):584-91 Nunn F, Cave TA, Knottenbelt C, Poxton IR. 2004 Association between Key-Gaskell syndrome and infection by Clostridium botulinum type C/D. Veterinary Record 155 111-115 Paris JK, Wills S, Balzer H-J, Shaw DJ, Danièlle A Gunn-Moore DA. 2014 Enteropathogen co-infection in UK cats with diarrhoea BMC Veterinary Research 10:13 Pham D.2009 Chronic intermittent diarrhea in a 14-month-old Abyssinian cat. Can Vet J. 2009 Jan;50(1):857. Thompson KA, Parnell NK, Hohenhaus AE, Moore GE, Rondeau MP. 2009 Feline exocrine pancreatic insufficiency: 16 cases (1992-2007). J Feline Med Surg. 2009 Dec;11(12):935-40. Epub 2009 Jun 23. Trepanier L. 2009 Idiopathic inflammatory bowel disease in cats. Rational treatment selection. J Feline Med Surg. 11(1):32-8. Trepanier L. 2010 Acute vomiting in cats: rational treatment selection. J Feline Med Surg. 12(3):225-30. Review.
Van Kruiningen H.J., Ryan M.J., Shindel N.M., 1983 The classification of feline colitis. J. Comp. Path. 93 275-294 Zanutto M de S, Hagiwara MK. 2007 Peritonite infecciosa em gatos relato de caso. Vet. Not., Uberlândia, v. 13, n. 2, p. 63-69. (In Portuguese)