Rabies Latency: Risks After Cat Scratch Injury

Q: Rabies Latency: Risks After Cat Scratch Injury

Dear Mr. <br>Jiang：<br>1. <br>The rabies virus is a rod-shaped virus belonging to the Lyssavirus genus. <br>All viruses in this genus share similar antigens, but monoclonal antibodies or nucleic acid sequencing can distinguish viruses from different regions or animal sources. <br

Rabies incubation period

Hello doctor, about six years ago I was scratched by a wild cat.
At that time, I was unsure if I received the rabies vaccine (because I heard that the rabies vaccine requires multiple doses; I remember I only received two shots, one for tetanus and I forgot the other).
I didn't pay much attention to it afterward, but later I heard that rabies can have an incubation period of up to 7 years.
Is it still possible for me to develop the disease after such a long time?

Jiang Xiansheng, 20~29 year old female. Ask Date: 2021/09/02

Dr. Xiao Yongxun reply Family Medicine

Dear Mr.
Jiang:
1.
The rabies virus is a rod-shaped virus belonging to the Lyssavirus genus.
All viruses in this genus share similar antigens, but monoclonal antibodies or nucleic acid sequencing can distinguish viruses from different regions or animal sources.
Animals infected with rabies carry the virus in their saliva, which can enter the human body through wounds caused by bites or scratches from infected animals (in rare cases, through freshly injured skin or mucous membranes).
It is also dangerous if an infected animal scratches a person, as animals tend to lick their paws.
2.
The incubation period for rabies typically ranges from 1 to 3 months, but it can be as short as less than a week or as long as over a year.
This duration depends on factors such as the severity of the wound, the density of nerve distribution in the wound area or its distance from the brain, the strain of the virus, the viral load, the degree of clothing protection, and other factors.
Initial symptoms of rabies are nonspecific and may include fever, sore throat, chills, malaise, anorexia, vomiting, respiratory distress, cough, weakness, anxiety, and headache, or specific symptoms related to the site of the bite or scratch.
After several days, symptoms of agitation and fear may develop, followed by paralysis, difficulty swallowing, and spasms of the throat muscles, leading to hydrophobia (also known as fear of water).
Subsequently, confusion and seizures may occur.
Without any medical intervention, patients typically die from respiratory paralysis within 2 to 6 days (sometimes longer).
3.
Regarding your statement that "rabies can have an incubation period of 7 years," I have not encountered any medical journal reports supporting this in clinical practice; I am unsure of the source of this information.
In cases of wild cat scratches or bites, current recommendations in our country suggest observing or capturing the cat for 10 days.
If the cat dies or shows signs of illness, the patient who was bitten or scratched should consider receiving the rabies vaccine.
In fact, this has been the policy of the World Health Organization for decades and has not been overturned or questioned.
After all, the rabies virus enters through the wound and typically reaches the central nervous system and causes illness within a few weeks to months; a 7-year incubation period would be highly unusual.
4.
If you have further questions, I recommend discussing them with your family physician before making any decisions.

Reply Date: 2021/09/02

More Info

Rabies is a viral disease that primarily affects mammals, including cats and dogs, and is transmitted through the saliva of an infected animal, typically via bites or scratches. The concern regarding rabies after a cat scratch injury, especially from a feral or stray cat, is valid, but it is essential to understand the nature of the disease, its transmission, and the associated risks.

Firstly, rabies has a well-documented incubation period, which is the time between exposure to the virus and the onset of symptoms. This period can vary significantly, typically ranging from a few weeks to several months, and in rare cases, it can extend up to a year or more. However, the idea that rabies can remain latent for several years, such as the seven years mentioned, is a misconception. While there have been anecdotal reports of very long incubation periods, these are exceedingly rare and not the norm. Most cases of rabies will present symptoms within a few months of exposure.

In your case, being scratched by a feral cat six years ago raises a few important considerations. If you did not receive the full rabies vaccination series after the incident, the risk of developing rabies is extremely low, especially if you have not experienced any symptoms in the intervening years. Rabies is almost universally fatal once clinical symptoms appear, and the absence of symptoms for such an extended period strongly suggests that you did not contract the virus.

Additionally, rabies is not transmitted through casual contact or through the air; it requires direct exposure to the saliva of an infected animal. If the scratch was superficial and did not involve deep tissue or significant bleeding, the likelihood of transmission would be even lower. Furthermore, rabies is not endemic in all regions, and in many places, including parts of Taiwan, the incidence of rabies in domestic cats is low due to vaccination programs and monitoring of wildlife reservoirs.

If you are still concerned about your past exposure, it is advisable to consult with a healthcare provider. They can assess your vaccination history and determine if any further action is necessary. In general, if you have not shown any symptoms of rabies after such a long period, it is highly unlikely that you are at risk.

In summary, while rabies is a serious disease, the risk of developing it from a cat scratch six years ago, especially without any symptoms, is minimal. Rabies vaccination protocols are designed to be effective when administered promptly after exposure, and the absence of symptoms over such a long period is reassuring. If you have ongoing concerns about your health or anxiety related to this incident, discussing these with a healthcare professional can provide peace of mind and appropriate guidance.

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