VetInfo Digest            June 2002

This Month:

Bite Wounds

          Dog Bites

          Cat Bites

          Humans Bitten by Pets

 

Feline Immunodeficiency Virus Vaccine

This Month's Note:

I have to be honest about the content of this month's newsletter. I was bitten in April by a cat who escaped from its owner's car as they pulled into our parking lot. The cat ran into the woods and I followed it, finally catching up to it as it hunkered down to decide its next move. I know that cat bite wounds are most likely to occur when a cat is picked up, so I knelt beside this cat and stroked its head several times prior to attempting to pick it up. Nothing about its reaction prepared me for the next few second's events. I said to the cat "I'm going to pick you up now", (who knows if they might actually understand more than we think) and then I reached under the cat. It immediately turned sideways to avoid being picked up, encountered my left thigh and bit me very deeply, actually tearing a fairly large hole in my pants. Then it decided the best escape route was up my chest and over my head. In self defense I put up both arms to protect my face and was bitten on my right hand at the base of my index and middle fingers. The cat got away.

Unfortunately, two dogs who had been attacked by a pack of larger dogs arrived at my clinic a few minutes later. I put on surgical gloves and repaired wounds on these dogs for about two hours. When I took off the surgical gloves it was obvious that the cat bite wounds were infected. Although I saw my physician shortly afterwards, it was too late to stop pretty severe complications. For approximately two weeks there was some question about whether permanent damage to the hand would occur. I did a lot of research on cat bite wounds in people during this time and it seemed reasonable to combine that with information on cat and dogs biting each other and to use it as the topic for this month's VetInfo Digest. So the motivation for this newsletter was almost entirely my own self interest!

 

Who Bit My Pet?

Many people come to our office whose pets have mystery bite wounds. Often, people ask me if a raccoon, opossum, or other wild animal made the bites. While it is not usually possible to determine the "biter" with precision, there is a general rule of thumb for bite wounds. In most cases, cats bite cats, dogs bite dogs and people bite people. This happens because cats are most likely to be associating with other cats, dogs with other dogs and so on. There are exceptions to this rule, just like most other rules, though.

When the source of a wound that appears to be inflicted by a bite is unknown, it is necessary to review the rabies vaccination history for the patient who has been bitten. In 2000, there were 114 confirmed cases of rabies in dogs and 249 confirmed cases of rabies in cats. For this reason, vigilance regarding the potential for rabies continues to be very important. It is critical for all dogs and cats to be vaccinated for rabies. The guidelines of the Compendium of Animal Rabies Prevention and Control calls for the euthanasia or 6 month quarantine, without any human exposure, of all pets bitten by a rabid animal who have not been vaccinated for rabies. Vaccinated pets need to be revaccinated immediately and kept under owner observation for 45 days. If a pet is bitten by an unidentifiable animal, the guidelines recommend assuming that rabies exposure has occurred. It is obviously preferable to have your pet vaccinated against rabies before a bite occurs.

 

General Bite Wound Information

Bite wounds are a common problem in veterinary practices. We examine more than a hundred bite wounds every year in our practice. In addition, at least once a year a member of our staff is bitten by a dog or cat and we routinely get phone calls from clients who have inquiries about their pet's vaccination status after a bite wound is inflicted by the pet. While I am not a medical doctor, the basic guidelines for bite wounds inflicted by dogs and cats are pretty well established in human medicine and I will include a review of them later in this issue.

It is extremely difficult to judge the severity of a bite wound based on the appearance of the skin wounds. For this reason, there are many varied views on appropriate care for bite wounds. Some veterinarians insist that every single bite wound should be surgically explored to determine the depth of the bite wound and damage to underlying structures. While this may be best from the standpoint of treating bite wounds it sometimes turns out to be a bad thing for a patient sensitive to anesthesia or severely stressed by the bite event. Therefore, most veterinarians assess the injuries and try to determine the probability that underlying structures are damaged. This information is combined with the assessment of the patient's general condition and a decision is made whether to open the wounds sufficiently to determine their depth. Whenever judgment calls are made there are going to be some errors. Remember that bite wounds can have serious complications and if it seems like your pet is not doing as well as expected after treatment for a bite, do not hesitate to ask your vet to reexamine your pet.

Surgical exploration of bite wounds is a fairly common practice, especially at veterinary emergency clinics. To explore a bite wound an incision is made that incorporates the bite wound and is long enough to allow visual inspection of the wound. The wound is opened to the depth of penetration to ensure that underlying structures are not damaged. If it becomes apparent that the bite has gone through the chest wall it may be necessary to take radiographs to check for lung collapse. If the tooth penetrated the body wall into the abdomen it may be necessary to open the abdomen to check for organ damage or to consider flushing the abdomen with saline and suctioning this saline out to check it for blood, fecal material or anything else that might indicate a more extensive problem.

After exploration of a dog bite wound the wound may be closed, usually with a drain placed prior to closure to allow any infection to be treated and drained. Sutures placed during this procedure are usually removed in 7 to 14 days and drains are removed most commonly in 2 to 5 days.

When a "drain" is used for a bite wound, it is usually a flattened tube of latex (Penrose drain) or other material that will keep the wound open to allow drainage around the tube. It is necessary to keep the wound clean to facilitate drainage.

When bite wounds are not explored it is very important to remember that there may be hidden damage. Severe swelling around bitten areas, death of the skin overlying bite wounds, a decrease in appetite, reduction in activity, breathing difficulties, jaundice or any other unusual symptoms after a bite wound should be reported to your veterinarian.

Small dogs and cats who are attacked by much larger dogs, or by multiple dogs, may have internal injuries from being shaken, even if there is very little external damage visible. Violent shaking of prey (in this case the smaller dog or cat) can cause the liver to fracture, separate kidneys from their blood supply, break the spinal cord or rupture the diaphragm. Any of these injuries can be fatal. It is vitally important to consider the potential for these types of injuries whenever a large dog shakes its victim, or when a large dog has been involved in an attack and the attack was not witnessed. Once in a while we even see these types of injuries when a big dog attacks another big dog, but they are less common in this case. If you see your pet being shaken by a larger attacker, please be sure to tell your vet.

Dog bite wounds become infected approximately 10 to 20% of the time, whether the dog bites a person, another dog or a cat. This is actually a low infection rate, presumably because dogs do not harbor highly infectious organisms in the mouths as frequently as cats. Cat bite wounds become infected somewhere between 35% and 60% of the time. There are times when we decide that antibiotics are not likely to be necessary when we are dealing with dog bite wounds but we usually choose to use antibiotics after a cat bite. When dogs or cats bite people it is a good idea to make sure that the person is adequately protected against tetanus by prior vaccination or to consider taking steps to protect against tetanus if vaccinations are not current.

 

Dogs Biting Dogs

The consequences of dog bites and dog attacks can be very severe, even when external damage appears minimal. On the other hand, fights between dogs can be very noisy and seemingly ferocious without any real damage occurring to either dog. There is a great deal of posturing and threatening, both verbal and physical before dogs begin to actually bite each other, in many instances. This is particularly true when two dogs are vying for a higher spot in their social order. If you only hear a fight between dogs it may be best to check to see if there is any evidence of wounds. Even a small puncture is potentially important but if there is no evidence of a wound at all it is possible that the "fight" ended with one dog giving in to the other without physical contact being made.

Some dogs do attack other dogs with the intent to cause harm. This can occur when a dog doesn't react appropriate to social signaling, when fear based or territorial aggression problems are present and when dogs turn their natural predatory behavior towards other dogs (most commonly much smaller dogs). In addition, there are dogs that are just mean. Aggression towards other dogs has been selectively encouraged through breeding in some breed lines and generalized aggressive tendencies are tolerated, or even encouraged, in other breeds.

It is helpful when thinking about the potential damage to categorize attacks based on the size and number of the dogs involved. When big dogs fight with each other the wounds may not be nearly so severe as when two or more big dogs attack one small dog. In a dog bite incident between large dogs it may not be necessary to explore completely a bite wound over a muscled body area, while a bite wound near a joint or on the chest wall might warrant a good surgical exploration of the wound to determine if the joint or chest have been damaged severely. When large dogs bite small dogs it is almost always best to surgically explore the wound and to consider chest X-rays to rule out diaphragmatic hernias and collapsed lungs and/or abdominal radiographs to try to rule out internal damage in the abdominal cavity.

Our clients sometimes have a hard time understanding how a small puncture wound in the skin can lead to a four or five inch tear in the muscle underlying the skin. Almost everyone realizes that skin can be moved from side to side several inches. To demonstrate this to yourself, just pick up a little fold of skin try to move it around. The skin itself will move an inch or so in most directions, so some tearing under the skin is possible based on this motion alone. Then think of a knife that has been pushed through a TupperwareÔ container full of JelloÔ. Is it possible to make a large cut in the JelloÔ by rocking the knife back and forth but to keep the cut in the plastic small? If you try you'll find out it is.

If you think of a dog's tooth as the knife, it makes sense that the skin can have a very small puncture but the underlying structures such as muscle, tendons or organs can be severely damaged. The longer the attacker's teeth are, the more damage they can do in this fashion. Once in a awhile a tooth breaks off during a biting episode and remains embedded in the injured dog. This can lead to chronic reoccurrences of infectious drainage or abscesses at the site of the dog bite wound. Anytime that chronic drainage from a bite wound is present it is best to explore the possibility of an embedded foreign body, such as a tooth, either surgically or with X-ray examination.

Dog bite wounds can also cause tissue injuries due to crushing tissue. Some dogs can exert pressure in excess of 400lbs/in2 when they bite. When this sort of pressure is applied to an area with underlying bone or tendon severe damage can occur in these tissues. Skin that is crushed during the biting episode may die and slough off after a few days. These types of injuries are not readily apparent at the time of the bite in many instances. Tissue that has been crushed sufficiently to disrupt the blood supply is more likely to become infected than undamaged tissue, so antibiotic therapy should be considered when it is obvious that a crushing wound has been inflicted.

One of the more important aspects of wound care for dog bite wounds is extensive irrigation of the wound. It is helpful to flush these wounds with large amounts of sterile saline solution or other fluid preparations suitable for wound cleansing. Sometimes we flush wounds to the point that clients think we are being excessive, but this is the best early line of defense against contamination and infection of the wound. After thorough flushing, most dog bite wounds can be closed surgically, if desired, without a great risk of infection, although it is not a good idea to close a wound in tissue that appears to be injured severely (crush injury). If there is damage to underlying tissues it is often necessary to place a drain in the injured area and run it to a place that drainage can occur. Deep puncture wounds are often left open in the hope that they will drain adequately on their own. It is also reasonable to allow most bite wounds to heal without suturing (by second intention), as long as they can be kept clean during the healing process.

When dog bite wounds become infected it is most likely due to staph infection and this will usually respond to treatment with amoxicillin and clavulanic acid (Clavamox Rx), cephalosporins or trimethoprim/sulfa combinations. If a choice was made to wait to see if infection occurred prior to using antibiotics it is best to obtain a specimen from the wound for bacterial culture and check for sensitivity to antibiotics so that the antibiotic choice can be adjusted if necessary.

 

Dogs Biting Humans

Between 1 and 2 million dog bites are reported to public health authorities in the United States each year. The number of unreported bites is estimated to be at least as high and perhaps higher. Cat bites are less common, accounting for about 10% of reported animal bites. Approximately 1 % of all visits to hospital emergency rooms are due to dog bites and most of these bites are inflicted by the family pet or neighbor's dog.

When dogs bite humans there is potential for severe wounds to occur, even if the dog is relatively small. Bites from large dogs have all the possible consequences discussed in the section on dogs biting dogs. Bites from small dogs are less likely to cause severe tissue damage, but infection can occur and even bite wounds from small dogs that occur on the hands or feet have the potential to cause debilitating injuries.

Antibiotic therapy is not always necessary for dog bite wounds. Many physicians do prefer to wait to see if infection will occur prior to using antibiotics when a dog bite has occurred, so it would not be unusual for your doctor to suggest this approach. It is imperative to have penetrating wounds of the hands and feet examined by a physician as they are more likely to become infected than wounds in most other areas and there is a strong potential for crushing injury of underlying tendons and joints that can have long term consequences if not dealt with properly in the initial stages of treatment. Tetanus vaccination may be necessary after a dog bite. Wounds on the face may be sutured, even if there has been several hours delay in seeking treatment.

Physicians tend to favor the use of amoxicillin/clavulanic acid ( Augmentin Rx) for both cat and dog bite wounds. Tetracyclines, such as doxycycline are used with patients might be sensitive to penicillins. Other antibiotics may be used, especially if a specimen is taken for bacterial culture and sensitivity. Dog bites are most commonly infected with Staphyloccocus aureus (Staph infection), but may drag almost any surface bacteria into a wound, so other infections are not uncommon.

Most states require dog bite wounds to be reported to the public health department. The usual practice after a dog bite is to quarantine the dog for ten days, to ensure that rabies virus was not transmitted by the bite. This works because rabies can only be transmitted in the last few days that an infected dog lives, so if a dog is still alive after ten days there is little to no chance of it having transmitted rabies, even it subsequently turns out that it is infected with the disease. If a bite from an unvaccinated dog occurs on the face or neck the health department may take the step of bypassing quarantine and asking for euthanasia of the dog so that it's brain can be examined for the presence of rabies virus. This is necessary because rabies virus travels from bite wound to the brain through the nervous system and wounds near the brain have a shorter incubation period as the travel distance along the nerves is very short.

There are approximately 12 to 15 deaths each year in the United States from the direct effects of dog attacks or complications associated with an attack. Most of these deaths occur in children. Over half of the dog bites reported in the U.S. are inflicted by the family pet. It is vitally important to consider the potential consequences of owning an aggressive pet and to seek help in dealing with aggressive behavior that is resulting in bite wounds. Consultation with a board certified veterinary behaviorist is probably best and it is worth making a very long trip to find such a specialist, if necessary. Certified animal behaviorists are also a reasonable choice but be very careful about taking advice from someone whose credentials are more along the lines of "I've trained hundreds of dogs". Don't make excuses for your dog. This is primarily a defense mechanism for people who wish to ignore the problem. If a dog bites anyone it is best to make a serious effort to discover why the bite occurred and to prevent any future instances of biting behavior.

 

Dogs Biting Cats

When dogs bite cats, the consequences are very similar to the big dog/small dog attacks discussed earlier. However, it is even more likely that a dog will shake a cat than another small dog, so particular attention has to be paid to the possibility of a diaphragmatic hernia. In addition, it is not unusual for dog bite wounds to penetrate the upper abdominal muscles near the big muscles along the spine. When this happens hernias through the bite wounds may show up weeks to months later in some cats. It is reasonable to take X-rays of the chest to rule out diaphragmatic hernia whenever there is any chance that a cat was shaken or jumped on during an attack by a dog and it is sometimes helpful to take them when there is external evidence of bite wounds over the abdomen. While it is not common, dog bites can also cause fractures of the face or limbs. When a bone fracture occurs due to a bite wound it necessary to use antibiotics to try to prevent bone infection (osteomylelitis). We find this to be particularly important when the bones overlying the sinuses are fractured, as chronic infections from these types of fractures seem to occur more frequently than with other types of fractures.

 

Cats Biting Cats

Cat bites are much different than dog bites. When cats bite they usually do not inflict crush damage and the smaller size teeth do not cause as much internal damage, although it is still important to consider damage to underlying muscle, especially when bites involve the abdominal musculature. The big problem with cat bites is infection. When cats bite each other infections are common and their bites infect other species, as well. The most common bacterial infection associated with cat bites is Pasteurella multocida, which can cause severe infections in as short a time as four to eight hours. Abscesses are common after cat bites and can show up within a day or two or may be delayed as long as several weeks after a biting incident. Bite wounds are the primary method by which feline immunodeficiency virus (FIV) is spread. For this reason, FIV infection is much more common in male cats than it is in female cats.

Most veterinarians dispense antibiotics when a cat is seen for cat bite wounds because of the high probability of infection occurring. This is particularly important when the wounds have occurred over areas in which the underlying bone is close to the surface or when wounds are near a joint. There are times when it is reasonable to wait and see if antibiotics are going to be necessary, though. If your veterinarian does not dispense antibiotics make sure that you know the procedure for getting in touch with him or her in case it becomes obvious that antibiotics were necessary. This is especially important when weekends or holidays are coming up. The antibiotic of choice for cat bites is probably the amoxicillin/clavulanic acid combination (Clavamox Rx), although some veterinarians currently favor fluoroquinolone antibiotics such as Baytril (Rx). It is not unusual for veterinarians to dispense amoxicillin alone, since the bacteria most likely to be causing the infection, Pasteurella multocida, tends to be susceptible to this antibiotic even without the addition of the clavulanic acid.

Unfortunately, many cat bite wounds are seen after they have already abscessed. The general signs that might indicate an abscess is present somewhere on the cat's body include depression, decrease in appetite, and pain that may be hard to localize in some instances. Specific signs include a warm or hot swelling under the skin, drainage of pus from a wound in the skin or even sloughing of a large piece of skin. It is not unusual for clients to bring their cat with a 1 to 2 inch hole in the skin, thinking that this area is the result of a fresh bite wound. On examination many of these types of wounds turn out to be ruptured abscesses in which skin necrosis (death) has occurred, causing the skin to fall off, leaving the large hole. In some cases the area of sloughed skin can be several inches across, especially when abscesses occur over the base of the tail. There is some controversy among veterinarians over the best way to handle cat abscesses. Many vets prefer to clean abscess sites well and leave them open, allowing them to heal over time. Usually even large abscess sites will heal within a week to two weeks. Other veterinarians prefer to clean out the abscess site surgically, remove any skin that looks like it might continue to slough off, place drains in the surgical site and then suture the skin. The thinking in this case is that a closed wound is easier to care for and more visually appealing.

We prefer to let these wounds heal open, but this is primarily an economic consideration. It is much less expensive to do this and we do not seem to have significant complications even with large wounds. If the aesthetic appearance of the wound is important and cost is not a consideration closing the abscessed area is usually a reasonable choice, though. Cats will occasionally have persistent recurrence of abscesses even with good cleansing of the abscess and proper selection of antibiotics. On rare occasions this occurs due to the presence of Mycobacterium species (the group that includes tuberculosis) or l-form bacterial infections. The l-form bacteria are an unusual mutant species that does not have a complete cell wall. Since disruption of the cell wall is how many commonly used antibiotics work, they don't have a lot of effect on these particular bacteria. Doxycycline, a tetracycline class antibiotic, is the drug of choice for l-form bacteria infections and is worth considering as an alternative antibiotic for chronic abscess prelims in cats.

I get asked about "feline AIDS" associated with bite wounds fairly frequently. Feline immunodeficiency virus (FIV) can cause acquired immune deficiency syndrome but is less likely to cause this effect than HIV is in humans. There is a lag period from the time a cat becomes infected with FIV until tests for it are positive, since this is an antibody test. If you have reason to be concerned about FIV after your cat is bitten by another cat it may be several months before it is possible to rule out infection with FIV.


Cats are exposed to rabies infection more commonly than dogs. It is vitally important to keep rabies vaccinations up to date for all cats that go outside. There are even occasional reports of indoor cats developing rabies, usually from exposure to bats. If rabies exposure is likely, or if your cat has a tendency to bite when frightened or disturbed, it is best to be sure that rabies vaccinations are kept current to reduce the hassle if or when your cat purposefully or accidentally bites someone.

 

When Cats Bite People and Dogs

Therapy for cat bite wounds for people and dogs are similar, so it just seemed easier to lump them together. Cat bites to humans are most dangerous when they occur on the hands and feet, or when the patient is immune compromised or has diabetes. Penetrating cat bite wounds of the hands should be examined by your physician. If your doctor suggests a referral to a hand surgery specialist it is best to go. Cat bite injuries that involve the tendon sheaths or surrounding compartments in the hand can cause permanent disability. I personally know a pet groomer who lost the use of her right hand permanently after a cat bite injury, despite prolonged and appropriate efforts to prevent infection and subsequent damage after the bite.

Cat bites over deep muscles, such as the thigh or upper arm are less likely to become infected and it is probably reasonable to wait and see if they will, although that would not be my preference if I was the one who was bitten.

The antibiotic of choice for cat bite wounds is the combination of amoxicillin and clavulanic acid (Augmentin Rx for humans, Clavamox Rx for pets). This is true if the cat bites a dog or a human. When patients are not able to take this antibiotic it is reasonable to use amoxicillin and cephalexin (Keflex Rx) in combination. If there is an allergy to penicillins it may be necessary to give clindamycin ( Cleocin Rx, Antirobe Rx) or doxycycline. The hallmark sign of a Pasteurella infection is the short duration between the bite and obvious signs of infection. If heat and swelling occur within 4 to 8 hours after the bite it is likely that a Pasteurella infection has occurred. If a cat bite occurs on the hand in an area in which damage to underlying tendons, joints or bones is possible, it is best to use antibiotics for at least 10 days. It can be a little difficult to convince some physicians and veterinarians that this is the case, since shorter periods of antibiotic therapy are routine for most other infections, including cat bite wounds in other locations.

 

Avoidance of Dog and Cat Bites.

Cats bite when they feel cornered with nowhere to escape. When cats are frightened and seeking escape routes they are more likely to think "three dimensionally" than dogs are. Remember that a cat bent on escape may see the easiest route to freedom as up --- and you may be the best climbing surface to get there. Try to avoid confrontations with cats who are frightened. Retreating and waiting for a better time to pick a cat up or move it is a good option, especially when the cat is not in imminent danger. It is rare for people to have or keep a truly aggressive cat, although there are a number of cats who bite hard in predatory play behavior. It is not at all unusual for stray or feral cats to be aggressive towards humans. It is best to simply avoid contact with cats you do not know.

It is best to bring your cat to your veterinarian's in a secure carrier, preferrably one designed specifically for a cat. The cardboard carriers that many pet stores and animal shelters send cats home in are OK for a short trip or two but are not really secure. At least once a year a client of ours loses their cat between getting out their car and getting to our front door. They may be frightened by a big dog in the parking lot, a low flying airplane, a truck backfiring or anything else they are not used to. When frightened, cats tend to run away. We can often catch them before any harm is done but there are great risks to a cat running around a parking lot or heading across the highway in front of the clinic. In addition there are risks to the cat's pursuers, who may be injured by a frantic or injured cat.

Dogs are more likely to be kept as pets even though there is some problem with aggression. Many dog owners appear to unaware that their dog is aggressive in certain situations. There are some things that you can do to decrease the chance of your dog biting or participating in a attack on another dog, cat or human.

1) Don't let your dog join a pack. Make SURE that isn't happening --- two dogs running together are three times as likely to get into trouble and the bigger the group the more the risk that aggressive pack behavior will occur.

2) Don't get between two dogs who are fighting. You can make the situation worse by seeming to support one dog over the other (making the underdog want to fight harder), severe unintentional injuries can occur when fighting dogs bite "helping" humans. If it seems likely that you will have to deal with a dog fight conflict, consider getting an airhorn or pepper spray made for dogs to break up the fights.

3) If your dog suffers from a condition that may cause chronic pain, such as hip dysplasia, dental disease, herniated discs or arthritis it may become very grumpy. Adequate pain control can make a big difference in a dog's outlook on life. Search for correctable sources of pain and consider good pain control as an option when aggression may be related to underlying pain.

4) Dogs should be on a leash when they are brought to the vet's and it is helpful if they have enough basic leash training that they can be lead into the veterinary office without jerking free from of the leash. If a dog is very aggressive, or very easily frightened, it may be best to talk with your veterinarian's receptionist about the possibility of getting an appointment first thing in the morning or towards the end of the day when fewer dogs and cats are likely to be present in the waiting room.

Cat bites account for about 10% of reported animal bites. Dog bites account for about 80 to 90% of reported bites and there are approximately 12 to 15 fatalities per year in the U.S. from dog bites, as well. Cat bites become infected between 30 and 60% of the time based on various reference sources . Dog bites become infected approximately 10 to 20% of the time. Even when infection does not occur the crushing injuries produced by bites can cause significant damage to tendons and joints. It is very important to have all penetrating dog and cat bite injuries examined by your physician and to have a recheck examination done whenever a bite involves a hand or is located in very close proximity to a joint or tendon. Any pain or loss of function still present 3 to 5 days after the initial wound should be reported to your physician.

 

Pet Owner Responsibility is the Key to Stopping Dog and Cat Bites!

Robert Frost said that "Goof fences make good neighbors" and that is especially true for neighbors who have aggressive dogs. Aggressive dogs must be controlled in such a way that they can not attack someone. Real fences are a good choice to prevent interaction with other dogs, cats and people. Walking your dog on a leash is best. Consider using a halter type collar (HaltiÒ or Promise CollarÒ so that you have more control. For really aggressive dogs a comfortable muzzle that can be worn at any time when biting might occur can prevent injury from bites. Travel with your cat in a cat carrier so that it doesn't bite out of fright if it gets loose from the car. Don't just warn guests of danger -- separate aggressive pets from them.

 

FIV vaccination from Ft. Dodge

Sometime this summer a new vaccination for feline immunodeficiency virus (FIV) will be available from the manufacturer, Ft. Dodge Laboratories, Inc.

This is in some ways a "break-through" product, since finding a vaccine for the lentivirus class of viruses has proven to be very difficult. It is unfortunate, but it does not appear at this time that the vaccination development will be able to carry over to human immunodeficiency virus since that virus is more prone to mutation than FIV.

This vaccination will be adjuvenated, which means that it will fall in the category of cat vaccines that are most suspect for causing vaccine associated cancers. This risk will have to be carefully weighed against the individual risk for FIV for each patient as part of the decision making process when choosing to vaccinate or not. Outdoor male cats are the most likely cats to develop FIV since it is spread primarily through bite wounds. Outdoor female cats would be next most likely and cats who live indoors alone, or with other cats not infected with FIV, are very unlikely to develop this infection. The combination of the vaccine and natural resistance is estimated to provide protection to about 76% of cats who are exposed to FIV after vaccination. The vaccine does cause antibody formation which interferes with the current tests, producing false positives in vaccinated cats. This is a significant problem for a vaccine that only provides partial protection, because it makes it very difficult to tell which cats are infected and which ones just have antibodies due to the vaccination.

Our initial thinking, likely to change as more information becomes available, is that we will try to restrict the use of this vaccine to outdoor cats with a high probability of being bitten but that we will be willing to use it in these cats. We have serious reservations due to the current inability to separate vaccinated from infected cats by testing, if we have used the vaccine and for this reason we are not likely to push hard for vaccination even in this group of cats, at least until this problem has been resolved.

 

Check the Subscriber Area Occasionally

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The VetInfo Digest is published by TierCom, Inc., P.O. Box 476, Cobbs Creek, VA 23035. The opinions expressed in this newsletter are those of Michael Richards, DVM., author. Please send e-mail for Dr. Richards to mervet@inna.net

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