Canine parvovirus | |
---|---|
Electron micrograph of canine parvovirus | |
Virus classification | |
(unranked): | Virus |
Realm: | Monodnaviria |
Kingdom: | Shotokuvirae |
Phylum: | Cossaviricota |
Class: | Quintoviricetes |
Order: | Piccovirales |
Family: | Parvoviridae |
Genus: | Protoparvovirus |
Species: | |
Virus: | Canine parvovirus |
Canine parvovirus (also referred to as CPV, CPV2, or parvo) is a contagious virus mainly affecting dogs and wolves. CPV is highly contagious and is spread from dog to dog by direct or indirect contact with their feces. Vaccines can prevent this infection, but mortality can reach 91% in untreated cases. Treatment often involves veterinary hospitalization. Canine parvovirus often infects other mammals including foxes, cats, and skunks. [1] Felines (cats) are also susceptible to panleukopenia, a different strain of parvovirus. [2]
Dogs that develop the disease show signs of the illness within three to ten days. The signs may include lethargy, vomiting, fever, and diarrhea (usually bloody). Generally, the first sign of CPV is lethargy. Secondary signs are loss of weight and appetite or diarrhea followed by vomiting. Diarrhea and vomiting result in dehydration that upsets the electrolyte balance and this may affect the dog critically. Secondary infections occur as a result of the weakened immune system. Because the normal intestinal lining is also compromised, blood and protein leak into the intestines, leading to anemia and loss of protein, and endotoxins escape into the bloodstream, causing endotoxemia. Dogs have a distinctive odor in the later stages of the infection. The white blood cell level falls, further weakening the dog. Any or all of these factors can lead to shock and death. Younger animals have worse survival rates. [3]
Diagnosis is made through detection of CPV2 in the feces by either an ELISA or a hemagglutination test, or by electron microscopy. PCR has become available to diagnose CPV2, and can be used later in the disease when potentially less virus is being shed in the feces that may not be detectable by ELISA. [4] Clinically, the intestinal form of the infection can sometimes be confused with coronavirus or other forms of enteritis. Parvovirus, however, is more serious and the presence of bloody diarrhea, a low white blood cell count, and necrosis of the intestinal lining also point more towards parvovirus, especially in an unvaccinated dog. The cardiac form is typically easier to diagnose because the symptoms are distinct. [5]
Survival rate depends on how quickly CPV is diagnosed, the age of the dog, and how aggressive the treatment is. There is no approved treatment, and the current standard of care is supportive care, involving extensive hospitalization, due to severe dehydration and potential damage to the intestines and bone marrow. A CPV test should be given as early as possible if CPV is suspected in order to begin early treatment and increase survival rate if the disease is found.
Supportive care ideally also consists of crystalloid IV fluids and/or colloids (e.g., Hetastarch), antinausea injections (antiemetics) such as maropitant, metoclopramide, dolasetron, ondansetron and prochlorperazine, and broad-spectrum antibiotic injections such as cefazolin/enrofloxacin, ampicillin/enrofloxacin, metronidazole, timentin, or enrofloxacin. [6] IV fluids are administered and antinausea and antibiotic injections are given subcutaneously, intramuscularly, or intravenously. The fluids are typically a mix of a sterile, balanced electrolyte solution, with an appropriate amount of B-complex vitamins, dextrose, and potassium chloride. Analgesic medications can be used to counteract the intestinal discomfort caused by frequent bouts of diarrhea; however, the use of opioid analgesics can result in secondary ileus and decreased motility.
In addition to fluids given to achieve adequate rehydration, each time the puppy vomits or has diarrhea in a significant quantity, an equal amount of fluid is administered intravenously. The fluid requirements of a patient are determined by the animal's body weight, weight changes over time, degree of dehydration at presentation, and surface area.
A blood plasma transfusion from a donor dog that has already survived CPV is sometimes used to provide passive immunity to the sick dog. Some veterinarians keep these dogs on site, or have frozen serum available. There have been no controlled studies regarding this treatment. [6] Additionally, fresh frozen plasma and human albumin transfusions can help replace the extreme protein losses seen in severe cases and help assure adequate tissue healing. However, this is controversial with the availability of safer colloids such as Hetastarch, as it will also increase the colloid osmotic pressure without the ill effect of predisposing that canine patient to future transfusion reaction.
Once the dog can keep fluids down, the IV fluids are gradually discontinued, and very bland food slowly introduced. Oral antibiotics are administered for a number of days depending on the white blood cell count and the patient's ability to fight off secondary infection. A puppy with minimal symptoms can recover in two or three days if the IV fluids are begun as soon as symptoms are noticed and the CPV test confirms the diagnosis. If more severe, depending on treatment, puppies can remain ill from five days up to two weeks. However, even with hospitalization, there is no guarantee that the dog will be cured and survive.
Kindred Biosciences, a biopharmaceutical company, is developing a monoclonal antibody as a prophylactic therapy to prevent clinical signs of parvovirus infection and also as treatment of established parvovirus infection. In 2021, Kindred Biosciences announced the completion of a pivotal efficacy study showing a 100% survival rate for dogs treated with KIND-030 compared to a 41% survival rate for dogs treated with placebo. [7]
Preliminary research in kidney cell lines have identified nitazoxanide, closantel sodium, and closantel as drugs which have the most potential as broad-spectrum antiviral agents against canine parvovirus and its various subspecies, raising the prospect that these drugs may yield potential for future treatments of this disease. [8] [9]
In May 2023, the USDA granted Elanco Animal Health conditional approval to develop a Canine Parvovirus Monoclonal Antibody (CPMA) which targets the virus instead of its symptoms. Initial distribution of CPMA to veterinarians began in July 2023. [10]
Parvovirus CPV2 is a relatively new disease that appeared in the late 1970s. It was first recognized in 1978 and spread worldwide in one to two years. [11] The virus is very similar to feline panleukopenia (also a parvovirus); they are 98% identical, differing only in two amino acids in the viral capsid protein VP2. [12] It is also highly similar to mink enteritis virus (MEV), and the parvoviruses of raccoons and foxes. [5] It is possible that CPV2 is a mutant of an unidentified parvovirus (similar to feline parvovirus (FPV)) of some wild carnivore. [13] CPV2 was thought to only cause diseases in canines, [5] but newer evidence suggest pathogenicity in cats too. [14] [15]
There are two types of canine parvovirus called canine minute virus (CPV1) and CPV2. CPV2 causes the most serious disease and affects domesticated dogs and wild canids. There are variants of CPV2 called CPV-2a and CPV-2b, identified in 1979 and 1984 respectively. [13] Most of canine parvovirus infection are believed to be caused by these two strains, which have replaced the original strain, and the present day virus is different from the one originally discovered, although they are indistinguishable by most routine tests. [16] [17] An additional variant is CPV-2c, a Glu-426 mutant, and was discovered in Italy, Vietnam, and Spain. [18] The antigenic patterns of 2a and 2b are quite similar to the original CPV2. Variant 2c however has a unique pattern of antigenicity. [19] This has led to claims of ineffective vaccination of dogs, [20] but studies have shown that the existing CPV vaccines based on CPV-2b provide adequate levels of protection against CPV-2c. A strain of CPV-2b (strain FP84) has been shown to cause disease in a small percentage of domestic cats, although vaccination for FPV seems to be protective. [17] With severe disease, dogs can die within 48 to 72 hours without treatment by fluids. In the more common, less severe form, mortality is about 10 percent. [12] Certain breeds, such as Rottweilers, Doberman Pinschers, and Pit bull terriers as well as other black and tan colored dogs may be more susceptible to CPV2. [21] Along with age and breed, factors such as a stressful environment, concurrent infections with bacteria, parasites, and canine coronavirus increase a dog's risk of severe infection. [3] Dogs infected with parvovirus usually die from the dehydration it causes or secondary infection rather than the virus itself.
The variants of CPV-2 are defined by surface protein (VP capsid) features. This classification does not correlate well with phylogenies built from other parts of the viral genome, such as the NS1 protein. [22]
Dogs become infected through oral contact with CPV2 in feces, infected soil, or fomites that carry the virus. Following ingestion, the virus replicates in the lymphoid tissue in the throat, and then spreads to the bloodstream. From there, the virus attacks rapidly dividing cells, notably those in the lymph nodes, intestinal crypts, and the bone marrow. There is depletion of lymphocytes in lymph nodes and necrosis and destruction of the intestinal crypts. [23] Anaerobic bacteria that normally reside in the intestines can then cross into the bloodstream, a process known as translocation, with bacteremia leading to sepsis. The most common bacteria involved in severe cases are Clostridium , Campylobacter and Salmonella species. This can lead to a syndrome known as systemic inflammatory response syndrome (SIRS). SIRS leads to a range of complications such as hypercoagulability of the blood, endotoxaemia and acute respiratory distress syndrome (ARDS). Bacterial myocarditis has also been reported secondarily to sepsis. [4] Dogs with CPV are at risk of intussusception, a condition where part of the intestine prolapses into another part. [3] Three to four days following infection, the virus is shed in the feces for up to three weeks, and the dog may remain an asymptomatic carrier and shed the virus periodically. [24] The virus is usually more deadly if the host is concurrently infested with worms or other intestinal parasites.
This form is less common and affects puppies infected in the uterus or shortly after birth until about 8 weeks of age. [3] The virus attacks the heart muscle and the puppy often dies suddenly or after a brief period of breathing difficulty due to pulmonary edema. On the microscopic level, there are many points of necrosis of the heart muscle that are associated with mononuclear cellular infiltration. The formation of excess fibrous tissue (fibrosis) is often evident in surviving dogs. Myofibers are the site of viral replication within cells. [5] The disease may or may not be accompanied with the signs and symptoms of the intestinal form. However, this form is now rarely seen due to widespread vaccination of breeding dogs. [24]
Even less frequently, the disease may also lead to a generalized infection in neonates and cause lesions and viral replication and attack in other tissues other than the gastrointestinal tissues and heart, but also brain, liver, lungs, kidneys, and adrenal cortex. The lining of the blood vessels are also severely affected, which lead the lesions in this region to hemorrhage. [5]
This type of infection can occur when a pregnant female dog is infected with CPV2. The adult may develop immunity with little or no clinical signs of disease. The virus may have already crossed the placenta to infect the fetus. This can lead to several abnormalities. In mild to moderate cases the pups can be born with neurological abnormalities such as cerebellar hypoplasia. [25]
CPV2 is a non-enveloped single-stranded DNA virus in the Parvoviridae family. The name comes from the Latin parvus , meaning small, as the virus is only 20 to 26 nm in diameter. It has an icosahedral symmetry. The genome is about 5000 nucleotides long. [26] CPV2 continues to evolve, and the success of new strains seems to depend on extending the range of hosts affected and improved binding to its receptor, the canine transferrin receptor. [27] CPV2 has a high rate of evolution, possibly due to a rate of nucleotide substitution that is more like RNA viruses such as Influenzavirus A. [28] In contrast, FPV seems to evolve only through random genetic drift. [29]
CPV2 affects dogs, wolves, foxes, and other canids. CPV2a and CPV2b have been isolated from a small percentage of symptomatic cats and is more common than feline panleukopenia in big cats. [30]
Previously it has been thought that the virus does not undergo cross species infection. However studies in Vietnam have shown that CPV2 can undergo minor antigenic shift and natural mutation to infect felids. Analyses of feline parvovirus (FPV) isolates in Vietnam and Taiwan revealed that more than 80% of the isolates were of the canine parvovirus type, rather than feline panleukopenia virus (FPLV). [31] CPV2 may spread to cats easier than dogs and undergo faster rates of mutation within that species.
CPV2 is an extremely virulent and contagious virus; the only reliable way to prevent infection is by vaccination. [32] Puppies are generally vaccinated in a series of doses, extending from the earliest time that the immunity derived from the mother wears off until after that passive immunity is definitely gone. [33] [34] Vaccines are performed starting at 7–8 weeks of age, with a booster given every 2–4 weeks until at least 16 weeks of age. Older puppies (16 weeks or older) are given at least two vaccinations 2 to 4 weeks apart. [33] The duration of immunity of vaccines for CPV2 has been tested for all major vaccine manufacturers in the United States and has been found to be at least three years after the initial puppy series and a booster 1 year later. [35]
A dog that successfully recovers from CPV2 generally remains contagious for up to three weeks, but it is possible it may remain contagious for up to six.[ citation needed ] CPV2 is an extremely resilient virus once it has been shed through the feces into the environment. CPV2 has been found to survive indoors for months and outdoors in moist environments years. [36] It can survive in extremely low and high temperatures, and is resistant to many chemical disinfectants. [36]
Canine distemper virus (CDV) is a viral disease that affects a wide variety of mammal families, including domestic and wild species of dogs, coyotes, foxes, pandas, wolves, ferrets, skunks, raccoons, and felines, as well as pinnipeds, some primates, and a variety of other species. CDV does not affect humans.
Carnivore protoparvovirus 1 is a species of parvovirus that infects carnivorans. It causes a highly contagious disease in both dogs and cats separately. The disease is generally divided into two major genogroups: FPV containing the classical feline panleukopenia virus (FPLV), and CPV-2 containing the canine parvovirus type 2 (CPV-2) which appeared in the 1970s.
Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.
Feline infectious peritonitis (FIP) is a common and aberrant immune response in cats to infection with feline coronavirus (FCoV).
The health of dogs is a well studied area in veterinary medicine.
Cerebellar hypoplasia (CH) is a neurological condition in which the cerebellum is smaller than usual or not completely developed. It has been reported in many animal species.
Uncinaria stenocephala is a nematode that parasitizes dogs, cats, and foxes as well as humans. It is rare to find in cats in the United States. Uncinaria stenocephala is the most common canine hookworm in cooler regions, such as Canada and the northern regions of the US, where it can be found primarily in foxes (40%). U. stenocephala is also one of the most common hookworms in the UK, called the northern hookworm, however it has a rather low prevalence. U. stenocephala is also considered to be zoonotic hookworms because they live in animals but can be transmitted to humans.
Canine coronavirus (CCoV) is an enveloped, positive-sense, single-stranded RNA virus which is a member of the species Alphacoronavirus 1. It causes a highly contagious intestinal disease worldwide in dogs. The infecting virus enters its host cell by binding to the APN receptor. It was discovered in 1971 in Germany during an outbreak in sentry dogs. The virus is a member of the genus Alphacoronavirus and subgenus Tegacovirus.
Infectious canine hepatitis (ICH) is an acute liver infection in dogs caused by Canine mastadenovirus A, formerly called Canine adenovirus 1 (CAV-1). Canine mastadenovirus A also causes disease in wolves, coyotes, and bears, and encephalitis in foxes. The virus is spread in the feces, urine, blood, saliva, and nasal discharge of infected dogs. It is contracted through the mouth or nose, where it replicates in the tonsils. The virus then infects the liver and kidneys. The incubation period is 4 to 9 days.
Canid alphaherpesvirus 1 (CaHV-1), formerly Canine herpesvirus (CHV), is a virus of the family Herpesviridae which most importantly causes a fatal hemorrhagic disease in puppies less than two to three weeks old. It is known to exist in the United States, Canada, Australia, Japan, England and Germany. CHV was first recognized in the mid-1960s from a fatal disease in puppies.
Hemorrhagic gastroenteritis (HGE) is a disease of dogs characterized by sudden vomiting and bloody diarrhea. The symptoms are usually severe, and HGE can be fatal if not treated. HGE is most common in young adult dogs of any breed, but especially small dogs such as the Toy Poodle and Miniature Schnauzer. It is not contagious.
Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by Felid alphaherpesvirus 1 (FeHV-1), of the family Herpesviridae. It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.
Carnivore bocaparvovirus 1, formerly Canine minute virus is a species of Bocaparvovirus of the family Parvoviridae that infects dogs. It is similar to bovine parvovirus in its protein structure and DNA. A virus causing respiratory disease in humans has been called human bocavirus due to its similarity to these viruses. Canine minute virus was originally discovered in Germany in 1967 in military dogs, although it was originally thought to not cause disease. Dogs and puppies are infected orally, and the virus is spread transplacentally to the fetuses. Symptoms are seen most commonly between the ages of one to three weeks and include severe diarrhea, difficulty breathing, and anorexia. In severe cases, illness can be fatal.
Vaccination of dogs is the practice of animal vaccination applied to dogs. Programs in this field have contributed both to the health of dogs and to the public health. In countries where routine rabies vaccination of dogs is practiced, for example, rabies in humans is reduced to a very rare event.
Animal viruses are viruses that infect animals. Viruses infect all cellular life and although viruses infect every animal, plant, fungus and protist species, each has its own specific range of viruses that often infect only that species.
Mink enteritis virus (MEV) is a strain of Carnivore protoparvovirus 1 that infects mink and causes enteritis. Like all parvoviruses, it is a small, spherical virus, and has a single-stranded DNA genome. The signs and symptoms of enteritis usually appear within 4–7 days after infection. The virus replicates in the cells of the crypt epithelium in the duodenum and jejunum and, to a lesser extent the ileum, colon and caecum. The severity of the disease is directly related to necrosis of the crypt epithelium.
DA2PP is a multivalent vaccine for dogs that protects against the viruses indicated by the alphanumeric characters forming the abbreviation: D for canine distemper, A2 for canine adenovirus type 2, which offers cross-protection to canine adenovirus type 1, the first P for canine parvovirus, and the second P for parainfluenza. Because infectious canine hepatitis is another name for canine adenovirus type 1, an H is sometimes used instead of A. In DA2PPC, the C indicates canine coronavirus. This is not considered a core vaccination and is therefore often excluded from the abbreviation.
Protoparvovirus is a genus of viruses in the Parvovirinae subfamily of the virus family Parvoviridae. Vertebrates serve as natural hosts. There are 15 species in the genus including Rodent protoparvovirus 1 for which the exemplar virus is minute virus of mice (MVM). This genus also includes canine parvovirus (CPV), which causes gastrointestinal tract damage in puppies that is about 80% fatal, and porcine parvovirus (PPV), which is a major cause of fetal death and infertility in pigs. The genus divides phylogenetically into two branches, one that contains many founder members of the family, such as MVM, CPV and PPV, which have been studied in considerable detail, and a second branch occupied exclusively by predicted viruses whose coding sequences were identified recently in the wild using virus discovery approaches, but whose biology remains minimally explored. This second branch currently contains two species whose members infect humans, called Primate protoparvovirus 1 and Primate protoparvovirus 3. Until 2014, the genus was called Parvovirus, but it was renamed to eliminate confusion between members of this genus and members of the entire family Parvoviridae.
Canine circovirus, first isolated in 2012, is a small non-enveloped, icosahedral, single-stranded DNA virus that infects domestic dogs and wild canids exclusively. It is a member of the Circoviridae family and the genus Circovirus. There are currently 11 species of known circoviruses that have been identified to affect a wide variety of birds and mammals. As seen with all extensively studied circoviruses, the diameter ranges between approximately 15 and 25 nanometers. The icosahedral triangulation number is 1, the smallest size a viral capsid can be, in which there are a total of 60 protein subunits that make up the capsid. CaCV is not to be confused with canine coronavirus, another diarrhea-causing agent within the family Coronaviridae, or porcine circoviruses which are a members of the same genus as CaCV but only seen in pigs. CaCV was the first Circovirus to be identified that infects a mammal species other than pigs.