This article began because I have found a number of people recommending Tamiflu as part of a treatment protocol for panleukopenia. I had heard of this before but my research could never find any decent resources on its use. I recently decided to research again and found a bit more information. Everything discussed here is sourced and I urge you to check out the original sources for more information. Again, this is not veterinary advice or even really advice at all.
What is Tamiflu?
Tamiflu is the brand name of the antiviral drug oseltamivir, a potent inhibitor of influenza virus neuraminidase. (Neuraminidase is a surface glycoprotein in influenza viruses.) However, the canine parvovirus (which developed from feline panleukopenia in the 1970s) has no neuraminidase.
However, it is hypothesized that oseltamivir may be acting on the neuraminidases of bacteria responsible for secondary bacterial infections. (Source) A 2013 article on Canine Parvovirus Enteritides by the same author that restates this hypothesis added a couple of other cautions. Their first concern was that “treatment of canine parvoviral enteritis with oseltamivir is the possibility of selection for resistant mutants among influenza viruses if widespread use of the drug occurs in veterinary clinics.” They also stated that “further investigation is required before the widespread use of oseltamivir can be recommended for treatment of CPV enteritis.”
This hypothesis is also seen in a 2005 article on Veterinary Partner, which was reviewed and revised in 2020. It states that “Because the parvovirus does not use neuraminidase in its replication, one might not expect oseltamivir to have value but it turns out that neuraminidase is an important enzyme used by pathogenic bacteria invading through the protective mucous barrier of the GI tract. This invasion through the mucous barrier is biochemically similar to the budding of virus from the cell membrane and oseltamivir is able to inhibit it. Invasion of intestinal bacteria into the bloodstream is an important cause of death in parvoviral infection and this is where oseltamavir appears to be helpful, though there is still controversy surrounding its use. Using oseltamivir in parvovirus infection has been shown to improve both weight gain and white blood cell counts in parvo-infected dogs.”
This article recommends giving oseltamivir as soon as a diagnosis is made and recommends “it may be possible to avoid the clinical disease by giving a course of oseltamivir.” However, they don’t given any reason or justification for suggesting this.
It is also unclear if the original article written in 2005 recommended Tamiflu or if this was an addition when the article was reviewed and revised. My guess is this was added later as the only study on Tamiflu was done later in 2010.
The 2010 Study
In 2010, a study of 35 dogs was done to determine if oseltamivir with standard therapy for canine parvoviral enteritis had any effect. To date, this seems to be the only study done. No study has been done on cats. The study was done with an incredibly small number of subjects, so it’s conclusions should be taken with a grain of salt. However, the study found that dogs given oseltamivir had gained weight during their hospitalization and did not have any “significant changes in their white blood cell (WBC) count.” And “major adverse effects were identified” with the use of it.
However, even this study stated that “role of oseltamivir in the treatment of parvoviral enteritis remains speculative.”
And while this study was published in 2010, it began as a Thesis by Michelle Savigny while at Texas A&M in 2008. And by accessing this thesis, you can get a little bit more information about the study. In this thesis, Savigny hoped that the use of Tamiflu would increase mortality and decrease hospitalization time. It did not.
However, in the discussion Savigny talks about the possible benefits of the weight gain. And it’s important to note that weight gain was something that was seen in other studies, including one on mice. And as Savigny notes “Other studies have shown that a significant change in weight in study subjects is also associated with an improved outcome.”
The 2017 Rice Article
The use of Tamiflu for the treatment of panleukopenia can also be linked to an article written by Jane Rice that was published in 2017. In this study, Rice talks about using Tamiflu with kittens under 2 pounds as “an alternate to metronidazole” or “if you have severe intestinal symptoms.” Metronidazole is an antibiotic and antiprotozoal agent that because it is bactericidal, it “as the potential to work faster and more efficiently than other antibiotics.” (Source)
She also states that “It has been postulated in parvo in dogs (a similar virus) the destruction of the intestinal crypt cells results in a breakdown in the normal protective intestinal barrier. Tamiflu protects the intestinal wall and is extra protection against bacteraemia.” And this seems to be the same hypothesis. But unfortunately, no research has been done to prove what everyone agrees is a hypothesis.
But it is important to note that Rice is not a veterinarian, and the paper was written after treating only 30 kittens. And this is the only article she has written on cats or kittens. So what she says should be taken with a grain of salt. (And for the record, I say the same thing about every article I have written so I’m not trying to be critical of her. But it’s important to evaluate the source as well as the source material.)
Neupogen?
But an important point that Rice makes is often overlooked: “[Tamiflu is] especially helpful in young kittens when Neupogen may be less helpful.” And it seems the article Rice wrote was more about the use of Neupogen, than Tamiflu. She even suggests that using Neupogen increases the survival rate of panleuk from 33% to 90%.
Neupogen is something that is rarely discussed regarding the treatment of panleukopenia and something that I will research further at a later date. (However, the University of Wisconsin doesn’t recommend it.)
But the problem with her conclusion is, by her own admission, she didn’t always treat cats and kittens the same. Sometimes she used metro, sometimes Tamiflu. With such a small sample, it would be impossible to draw any conclusions.
My Conclusions
In my opinion, should you use Tamiflu as a treatment of panleukopenia? To be honest, I don’t know. I have not seen anything that would cause harm, but I also don’t see it as something that is a miracle cure or even a preventative unless it is able to help boost a cat’s immune system. Tamiflu doesn’t kill or harm that parvovirus that causes panleukopenia, which is clear based on the evidence. I will point out in a 2017 ASPCA webinar on panleukopenia presented by Stephanie Janeczko (DVM, MS, DABVP, CAWA Senior Director of Community Outreach Shelter Medicine Programs), Tamiflu was not recommended in the treatment of panleukopenia. This webinar directly references the 2010 study on dogs. So at least one expert looked at the evidence and decided against recommending it.