CONTROL & MANAGEMENT OF PARVOVIRUS INFECTION IN DOGS

Parvovirus is an incredibly contagious disease that spreads quickly and efficiently. So how exactly does it spread?

While canine parvovirus is not airborne, it can be found on many surfaces within the environment.

It is spread by contact with contaminated feces, but you don’t have to see solid feces for the virus to be present. It can live on the ground or on surfaces in kennels, on peoples’ hands, or on the clothing of people that have been contaminated. Dogs could also carry it on their fur or paws if they have come into contact with contaminated fecal material.

Parvovirus can live outdoors for months, if not years, and is resistant to many disinfectants, although it is susceptible to diluted bleach and some specialized cleaners commonly used in veterinary hospitals.

Cats also have a type of parvovirus that causes severe disease, known as feline panleukopenia.

While dogs cannot get feline parvovirus from cats, cats can become infected with canine parvovirus. They most often have much more mild clinical signs than dogs do, but there is a strain of canine parvovirus that can cause severe illness in cats.

Diagnosis of canine parvovirus is made on the basis of clinical signs and a history of poor vaccination protocol, or lack of vaccination history, along with conformation using a faecal antigen test (parvovirus “snap” tests). In addition, because there are many other diseases that may also result in similar clinical signs, a thorough evaluation of the patient must be performed .

Stages of Parvo?:-

The stages of canine parvovirus follow the stages of most viral infections.

1. Infection

The puppy (or adult dog) is exposed to viral particles via fecal material from an infected dog. These viral particles can come from a few places:

• The environment, on the ground or on a surface

• The mother dog

• People/clothing/inanimate objects that came into contact with the feces of an infected dog

Only a very small amount of fecal material is necessary to cause infection, which enters through the mouth of the puppy or dog.

2. Incubation

There is an incubation period (between three and seven days) in which the dog is infected with parvovirus but not yet showing symptoms.

During this period, the virus specifically seeks out the most rapidly dividing cells in the body—typically, it starts attacking the tonsils or lymph nodes of the throat. By targeting these rapidly dividing cells, the virus is able to multiply effectively and efficiently and invade other parts of the dog’s system.

Once it has multiplied and entered the bloodstream, the virus will seek out other sources of rapidly diving cells. The most hard-hit areas are:

• Bone marrow

• Cells that line the walls of the small intestines

In small puppies, parvovirus can also infect the heart, which causes inflammation of the heart muscle, poor heart function, and arrythmias.

3. Illness

When the virus infects the bone marrow, it attacks the young immune cells, which leads a drop in protective white blood cells.

This weakens the body’s ability to protect itself and allows the virus to more easily invade the gastrointestinal (GI) tract. This is where the worst damage happens. The virus attacks the lining of the small intestine, which prevents the dog’s GI tract from being able to:

• Absorb nutrients

• Prevent fluid loss into the stool

• Prevent bacteria from moving into the gut

This leads to serious health issues, such as:

• Diarrhea

• Vomiting

• Lethargy

• Severe dehydration

• Fever

• Possibly sepsis

While parvo in dogs is not always fatal, those that do not survive typically die from dehydration or shock—along with the damage caused by the septic toxins from the intestinal bacteria escaping into the bloodstream.

4. Recovery

Recovery from parvovirus varies case by case. Full recovery may take quite a while depending on the severity of the disease and the damage it has done.

Dogs that can recover from infection are sick for five to 10 days after symptoms begin.

It is very important that puppies with parvovirus receive adequate nutrition so that their intestines can heal.

Dogs recovering from a parvo infection should be fed a bland, easily digestible diet. Hill’s, Purina, and Royal Canin all make prescription veterinary diets that are carefully formulated to be nutritionally balanced and gentle on the GI tract.

A puppy recovering from canine parvovirus will require special care to help facilitate a complete and successful recovery. Upon returning home, your puppy will be finishing up a course of antibiotics and may also be on some medication for nausea or diarrhea. It is very important that you give your puppy the medication prescribed for the full amount of time it has been prescribed; even if he seems fine.

Your puppy is recovering from some extensive damage to his/her intestinal tract. It is typical for stools to be a little loose at first or for no stool to be produced for a few days as the intestinal tract recovers. The stool should gradually firm up over the first 3-5 days at home and your puppy should be active, and exhibiting his normal demeanor and behavior. If the diarrhea persists, if vomiting occurs or if your puppy seems depressed, please contact your veterinarian at once for instructions on any additional treament that may be necessary

Diet:-

Your puppy’s appetite may seem ravenous after going so long without food. However, do not allow the puppy to gorge or overeat, as this can result in more vomiting or diarrhea. Feed smaller meals separated by at least an hour or two. Gradually increasing your puppy’s food consumption will allow his system to better handle the increased food levels without becoming overwhelmed. While your puppy is recovering it is important to make sure you do not feed table scraps. Stick to the diet recommended by your veterinarian. A prescription diet may be recommended or home cooked diet may be recommended (such as boiled chicken and white rice, or fat free cottage cheese and pasta). It is important for your puppy’s food to be easily digestible, so stick to the protocol your veterinarian has recommended.

The Traditional Nutritional Approach:

Traditionally, interventions used in parvoviral enteritis patients include the practice of placing the patient on NPO, or nil per os (“nothing by mouth”), treatment for 24 to 72 hours, preventing any food from entering the gastrointestinal tract.While the application of NPO treatment is common, growing evidence indicates that early implementation of enteral nutrition is beneficial for patients with a variety of gastrointestinal diseases, including canine parvoviral enteritis.

A number of longstanding reasons advocate for an NPO strategy in a patient that is exhibiting gastroenteritis with signs of vomiting and diarrhea:

1. It has been thought that the presence of food in the gastrointestinal tract can delay recovery by stimulating intestinal contractions and increasing frequency of defecation, thereby increasing patient discomfort, and that fasting allows the bowel to rest.

2. The introduction of food is thought to stimulate further vomiting in animals with gastroenteritis, which can lead to higher chances of aspiration.

3. Undigested food in the gastrointestinal lumen is thought to serve as nutrition for bacteria, leading to further proliferation of detrimental microbes.

4. The presence of food in the gastrointestinal lumen can draw exudate into the lumen through osmosis and exacerbate diarrhea.

5. Offering food to a patient that is nauseated and feeling ill can lead to food aversion, delaying the return of appetite when the patient is ready to eat.

Exercise:-

Your puppy should be considered contagious to other puppies for at least a month, so it is important to “play it safe” by restricting trips to the park, obedience school or other neighborhood areas where other puppies may be present. If your puppy is less than 16 weeks of age, he/she should not be allowed in public areas until the vaccination series is fully completed.

Other Pets:-

Cats and humans are not susceptible to canine parvovirus infection. Adult dogs that have been vaccinated are also not susceptible; however. puppies are at risk. If your sick puppy was indoors only, wait at least one month before any new puppies come to your home. If your sick puppy was outdoors, remember that it can take up to 7 months before the virus is eliminated from soil.

Bathing:-

Your puppy may be bathed any time as long as you do not allow him/her to get cold or chilled after the bath. Bathing will reduce the amount of virus left on the puppy’s fur and will help reduce contagion.

Resuming Vaccines:-

Follow your veterinarian’s recommendations on resuming vaccines. Your puppy cannot be re-infected with this virus for at least 3 years (and probably is protected for life simply by virtue of this infection), but there are other viruses that your puppy should be protected against. Your veterinarian will give you a vaccination schedule to adhere to for the future to help protect your dog against future infections.

There should be no permanent ramifications due to this infection. The recovered puppy should lead a normal life once the recovery period is completed (approximately 1-2 weeks).

There is very little specific therapy that can be directed against the parvovirus virus itself by the time clinical signs of illness are evident. Treatment therefore remains supportive for the vast majority of patients clinically affected with signs of parvovirus gastroenteritis. In general, fluid therapy, analgesia, intestinal support and nutrition form the basis for successful patient management.

A suggested treatment rationale follows…

1. Intravenous Fluid Therapy – in most patients presenting to the veterinary clinic with vomiting and diarrhoea, the presumption is that the patient will have lost suficient Fluids to have become dehydrated, even if this is not clinically apparent. Restoration of this Fluid deficit is required to prevent further gastrointestinal injury, and patient hemodynamic compromise and renal injury. Fluid therapy is administered in the following manner: a. Correction of intravascular volume deficits – for patients displaying symptoms of shock or haemodynamic compromise, such as those with weak pulses, tachycardia, bradycardia, collapse, tacky mucous membranes etc., initial Fluid resuscitation should begin with rapid intravenous administration of a balanced isotonic crystalloid solution such as Lactated Ringers Solution, or normosol-R. Initial Fluid rates should be suficient to correct intravascular volume deficits within one hour of patient presentation. !e authors’ preference is to administer an isotonic crystalloid in boluses of 7-12 ml/kg IV over 10 minutes, followed by patient reassessment, and for this procedure to be repeated until signs of haemodynamic compromise are no longer present – as evidenced by a return of normal pulse quality, improvement in capillary refill time, improved mentation, normal heart rate etc. If significant haemodynamic improvement is not noted within 30 minutes of fluid therapy, a bolus of synthetic colloid such as hydroxy-ethyl starch (Voluven) or Pentaspan is administered at a dose of 3-5 ml/kg, given intravenously over 10 minutes to prolong the efectiveness of isotonic crystalloid therapy within the intravascular space.

b. Following correction of intravascular volume defecits, the patients hydration de”cit is calculated (hydration deficit volume (ml) = % dehydration (e.g. 5% = 0.05) x bodyweight(kg) x 1000), and this volume of fluid is administered to the patient over 8-24 hours, in addition to the patients’ normal daily fluid requirement (60 ml/ kg/24hrs). Typically, fluid required to replace hydration deficits is similar in composition to extracellular fluid, but should be supplemented with potassium, to replace renal and gastrointestinal loss of potassium. An ideal fluid for replacement of hydration de”cits is Lactated Ringers Solution, supplemented with 20-30 mEq/L potassium chloride. c. Following correction of hydration de”cits, the patient requires uid therapy for maintenance of normal body functions, PLUS replacement of ongoing uid losses through the gastrointestinal tract, in patients that continue to have diarrhoea and/or vomiting. In most cases, a uid type such as Lactated Ringers Solution, with 5% glucose, and 20-30 mEq/L potassium chloride is required. In patients without signifcant gastrointestinal fuid loss, 0.45% sodium chloride solution, 2.5% glucose, and 20-30 mEq/L potassium chloride is usually suficient to meet ongoing uid requirements. In patients with significant loss of gastrointestinal uid, blood or protein, a combination of isotonic crystalloid and colloid therapy, using hydroxy-ethyl starch, Pentaspan, or blood or fresh frozen plasma transfusion is required, in order to maintain blood volume, hydration status, and colloid oncotic pressure necessary for tissue oxygen delivery to body tissues. d. Plasma and synthetic colloid use: Patients with parvovirus enteritis are high risk, critically ill patients that frequently sufer from significant losses of plasma proteins into the intestinal lumen. This can lead to hypoproteinaemia, hypoalbuminaemia, and, occasionally, coagulation abnormalities. The use of fresh frozen plasma and/or synthetic colloids in these patients is controversial, but it also has sound rationale. Hypoproteinaemia and hypoalbuminaemia are negative prognostic indicators in patients with severe illness. They are associated with decreased efective circulating blood volume, poor tissue perfusion, and worse outcome. Administration of fresh frozen plasma can reasonably be considered in any patient with parvovirus enteritis that is critically unwell. Optimum benefit from transfusion is obtained when transfusion is administered early in the course of disease, at dose rates of 10-30 ml/kg intravenously over four to six hours. Following plasma transfusion, synthetic colloids such as hydroxy-ethyl starch or Pentaspan may be administered at a rate of 10 ml/kg/day in addition to fuid therapy to provide for maintenance and ongoing losses.

2. Dietary management – Nil per Os (NPO) for an initial six to twelve hour period following admission to hospital may be beneficial in most cases of diarrhoea in dogs and cats. NPO decreases the number of osmotic particles available in the intestinal lumen contributing to osmotic diarrhoea, and allows more rapid re-growth of intestinal villi, and resumption of intestinal function. Following an initial short period of bowel rest, micro-enteral nutrition should commence. Micro-enteral nutrition, using glucose, hydrolyzed proteins and isotonic electrolyte solutions, such as Lectade or Vytrate, have been shown to maintain intestinal mucosal health, reduce atrophy of the intestinal lumen cells, and improve recovery rates from diarrhoea. The rate of administration is 1-2 ml/kg/hr. These solutions may be used in the presence of ongoing vomiting and diarrhoea, as they are readily absorbed by gastric mucosal cells, and enterocytes, even in the presence of disease. Following 12 hours of micro-enteral nutrition, more

complex nutritional formulations should be fed to the patient – typically by nasogastric or oesophagostomy tube. On resumption of feeding, a low fat, high biological value protein, primarily carbohydrate diet should be fed. The carbohydrate present in rice is best because its starch is more completely assimilated than other carbohydrate sources. Select a lean protein source such as chicken. Veterinary prescriptions diets such as Hill’s i/d diet are ideal for this purpose.

3. Motility modi!cation – narcotic analgesics – loperamide (Imodium), Diphenoxylate (Lomotil) – increase segmental bowel contractions, and have been used for symptomatic management of acute diarrhoea. they should not however be used in patients with infectious diarrhoea caused by bacteria or viruses, as they have been shown to prolong illness, and delay clearance of intestinal bacterial toxins.

4. Protectants and absorbents – kaolin/pectin, charcoal, and barium sulphate – have questionable eficacy. Bismuth subsalicylate is the most useful, as is has anti-enterotoxin, antibacterial, anti-secretory and anti-inflammatory effect, and has been used as an adjunct to therapy, but is not considered essential in most cases.

5. Antibiotics – are usually not indicated except in cases of immunosuppression, fever, leukocytosis, leukopaenia, malena, haematochezia, and shock. Initial antibiotic choices for diarrhoea include antibiotics effective against enteric bacteria – usually a combination of mixed aerobic and anaerobic, gram positive and gram negative bacteria. First generation cephalosporin antibiotics are commonly used at a dose of 22 mg/kg IV q 8 hrs. Alternatively, for aerobic infections, enrofloxacin at 5 mg/kg SC q 24hrs is effective. For anaerobic infections, metronidazole is the preferred agent, at 20 mg/kg IV q 24 hrs.

6. Anti-emetic therapy – anti-emetic therapy using metoclopramide, maropitant, Ondansetron or dolasetron may be used in patients that have persistent vomiting not caused by intestinal obstruction, in order to minimize fluid loss from the patient, and to improve patient comfort. Some clinicians insert naso-gastric tubes to remove gastric secretions as an adjunct to the use of anti-emetics, and to facilitate administration of micro-enteral nutrition. The use of these tubes is associated with a dramatic reduction in nausea and vomiting – particularly in puppies with parvovirus enteritis and in patients with pancreatitis.

7. Analgesia – Opiate analgesics such as butorphanol or fentanyl are preferred in most cases of acute infectious gastroenteritis, and should be administered by continuous infusion for optimum benefit for the patient. Non-steroid anti-inammatory drugs or steroid anti-inammatory drugs are contraindicated in most cases of acute infectious diarrhoea because they decrease blood ow to the gastric mucosa, and can result in intestinal ulceration and acute renal failure – particularly in dehydrated patients. For the most part, this supportive care will ensure optimum conditions or opportunity for gut function to return to normal, once the underlying infectious cause resolves. Obviously, it is important in any patient to support airway, respiratory function, neurological function and renal perfusion with intravenous uid therapy, oxygen therapy and other supportive measures.

Reference-On Request