犬细小病毒（CANINE PARVOVIRUS）
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Canine parvovirus type 2(CPV2，colloquioally parvo)is a contagious virus maiMy affecting dogs． The disease is highly infectious and is spread from dog to dog by direct or indirect contact with their feces．It can be especially severe in puppies that are not protected by maternal antibodies or vaccination．It has two distinct presentations，a cardiac and intestinal form．The common signs of the intestinal form are severe vomiting and severe haemmorhagic(bloody)diarrhea．The cardiac form causes respiratory or cardiovascular failure in young puppies．Treatment often involves veterinary hospitalization．Vaccines can prevent this infection，but mortality can reach 91％in untreated cases． There are two types of canine parvovirus called canine minute virus(CPVl)and CPV2．CPV2 causes the most serious disease and affeCtS domesticated dogs and wild canids．There are variants of CPV2 called CPV一2a，CPV一2b and CPV一2c．Types 2a and 2b are distinct from the original CPV type 2 in terms of virulence and their ability to infect and cause disease in cats t00． CPV——2c is a newly identified variant similar to 2b．The viral protein of 2c contains one amino acid different from CPV-2b but it is believed this could be significant． 2c strains have been identified in parts of Europe，the Americas and in Asia．Emergence of this strain has led to claims of ineffective vaccination of dogs，however studies have shown that the existing CPV vaccines still provide adequate levels of protection against CPV cype 2c． History cPv2 is a relatively new disease that appeared in the late l 970s．It was first recognized in l 978 and spread worldwide in one to two years．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．It is also highly similar to mink enteritis， and the parvoviruses of raccoons and foxes．The early belief was that the feline panleukopenia mutated into CPV2．Although this has not been proven，the strong similarity to feline panleukopenia makes this the most credible theory．However，it is possible that CPV2 is a mutant of an unidentified parvovirus (similar to feline parvovirus(FPV))of some wild carnivore． A strain of CPV一2b(strain FP84)has been shown to cause disease in a small percentage of domestic cats，although vaccination for FPV seems to be protective． CPV2，however，does not cause disease in cats and does so only mfldly in mink and raccoons，and is a virus almost exclusively affecting canines． Two more strains of canine parvovirus CPV——2a and CPV-2b were identified in l 979 and l 984 respectively．Most cases 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^%~ H+u-^G.b)@0
.[tpb8@(G)Q0indistinguishable by most routine tests．A third type，CPV一2c (a Glu一426 mutant)，has been discovered in Italy，Vietnam，and Spain． Virology CPV2 is a non——enveloped single——stranded DNA virus．The name comes from the Latin parvus， meaning small，as the virus is only 20 t0 26 nm in diameter．It has an icosahedral symmetry．The genome is about 5000 nucleotides lon9．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．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．In contrast，FPV seems to evolve only through random genetic drift． CPV2 affects dogs，wolves，foxes，and other canids．CPV-2a and CPV-2b have been isolated from a small percentage of symptomatic cats and is more common than feline panleukopenia in big cats． Previously it has been thought that the virus does not undergo cross species infection．However studias 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 ffline panleukopenia virus(FPLV)．CPV2 may spread to cats easier than dogs and undergo faster rates of mutation within that species．The virus does not transmit to birds，or humans，but it can be spread by them when a bird comes in contact with feces and then the dog's environment，or when a cat goes to the groomers and returns with an exposed pet carrier． Variants There are variants of CPV type 2 called CPV一2a． CPV一2b and CPV一2c．The antigenic patterns of 2a and 2b are quite similar to the original CPV type 2．Variant 2c however has a unique pattern of antigenicity．This has led to claims of ineffective vaccination of dogs，but studies have shown that the existing CPV vaccines based on CPV type 2b，provide adequate levels of protection against CPV type 2c．However，there are reports that out&ted vaccines based on the old CPV——type 2 may not afford sufficient cross—— protection against the type 2c variant． Pathophysiology There are two forills of CPV2：intestinal and cardiac．Puppies are most susceptible，but more than 80 percent of adult dogs show no symptoms． With severe disease，dogs can die within 48 t0 72 hours without treatment by fluids and antibiotics． In the more common，less severe form，mortality is about l o percent．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．Mong 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．Dogs who catch Parvovirus usually die from the dehydration it causes or secondary infection rather than the virus itself． Intestinal forill Dogs become infected through oral contact with中国宠物医师网[ G `7d8N3t
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z0a0CPV2 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 1、，mph nodes and necrosis and destruction of the intestinal crypts．Anaerobic bacteria that normally reside in the intestines can then CROSS into the bloodstream，a process known as translocation， and cause sepsis．The most common bacteria involved in severe cases are Clostridia， Campylobacter and salmonellaspecies．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．Dogs with CPV are at risk of intussusception，a condition where part of the intestine prolapses into another part．Three to four days following infection，the virus is shed in the fec：es for up to three weeks，and the dog may remain an asymptomatic carrier and shed the virus periodically．The virus is usually more d eadly when infested with wOITnS or other intestinal parasxtes- Cardiac form T11is f0肌is less common and affects puppies infected in the uterus or shortly after birth until about 8 weeks of age．The vims attacks the heart muscle and the puppy often dies suddenly or after a brief period of breathing difficulty．On the microscopic level．there are many points oi 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．The disease may or mav not be accompanied with the signs and svmptoms of the intestinal form．However，this form is now rarely seen due to widespread vaccination of breeding dogs． 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，fiver，lungs，kidneys，and adrenal cortex．The lining of the blood vessels are also severely affected，which lead the lesions in this region to hemorrhage． Infection in the uterus 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 villLls may have already crossed the Dlacenta to infect the foetus．This can lead to several abnormalities．In severe cases the pups can be stiu bom or born mummified，in mild to nloderate cases the pups can be born with neurological abnormalities such as cerebellar hypoplasia． Signs and symptoms Dogs that develop the disease show symptoms ot the illness within 5 t0 1 0 days．The symptoms include lethargy，vomitin9，fever，and diarrhea (USUally bloody)．Diarrhea and vonutlng result in dehydration and secondary infections can set in· Due to dehydration，the dog's electrolyte balance can become critically affected．Because the normal intestinal lining is also compromised，blood and
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-`0N z0X0N0CPV2 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．Anaerobic bacteria that normally reside in the intestines can then cross into the bloodstream，a process known as translocation， and cause sepsis．The most common bacteria involved in severe cases are Clostridia， Campylobacter and salmonellaspecies．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．Dogs with CPV are at risk of intussusception，a condition where part of the intestine prolapses into another part．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．The virus is usually more deadly when infested with worms or other intestinal parasites． Cardiac form This form is less common and affects puppies infected in the uterus or shortly after birth until about 8 weeks of age．The virus attacks the heart muscle and the puppy often dias suddenly or after 一 一一。4Q h/w p!R9`$HM0n0
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a brief period of breathing difficulty．On the microscopic level，there are many points of necrosl’s of the heart muscle that are associated with mononuclear cellular inflltration．The formation of excess fibrous tissue(fibrosis)is often evident in surviving dogs．Myofibers are the site of viral replication within cells．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． 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，fiver，lungs，kidneys，and adrenal cortex．The lining of the blood vessels are also severely affected，which lead the lesions in this region to hemorrhage． Infection in the uterus 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 vims may have already crossed the placenta to infect the foetus．This can lead to several abnormalities．In severe cases the pups can be still born or born mummified，in mild to moderate cases the pups can be born with neurological abnormalities such as cerebellar hypoplasia． Signs and symptoms Dogs that develop the disease show symptoms of the illness within 5 t0 1 0 days．The symptoms include lethargy，vomitin9，fever，and diarrhea (usually bloody)．Diarrhea and vomiting result in dehydration and secondary infections can set in． Due to dehydration，the dog's electrolyte balance can become critically affected．Because the normal intestinal lining is also compromised，blood andGP fB0F? Y0
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protein leak into the intestines leading to anemia and loss of protein，and endotoxins escaping 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 d09．Any or all of these factors can 1ead to shock and death Diagnosis Diagnosis is made through detection of CPV2 in the feces by either an EIA 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 EIA．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 d09．The cardiac form is typically easier to diagnose because the symptoms are distinct． Prevention and decontamination Prevention is the only way to ensure that a puppy or dog remains healthy since the disease is extremely virulent and contagious．The virus is extremely hardy and has been found to survive in feces and other organic material such as soil for over a year．It survives extremely cold and hot temperatures．The only household disinfectant that kills the virus is bleach． Weanin ’ can be vaccinated with aeanmg puppies modified live virus low passage high titer vaccine at 6 weeks of age，then every 3 t0 4 weeks until 1 5 0r 1 6 weeks．Puppies are initially protected through passive immunity derived from the mother．These maternal antibodies wear off before the puppy's immune system is mature enough to fight off CPV2 infection．Maternal antibodies also interfere with vaccination for CPV2 and can cause vaccine failure．Thus puppies are generally vaccinated in a series of shots，extending from the earliest time that the immunity derived from the mother wears off until after that passive immunity is definitely gone．Older puppies(1 6 weeks or older)are given 3 vaccinations 3 t0 4 weeks apart． 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 l year later． A dog that successfully recovers from CPV2 sheds virus for a few days．Ongoing infection risk is primarily from faecal contamination of the environment due to the virus's ability to survive many months in the environment．Neighbours and family members with dogs should be notified of infected animals so that they can ensure that their dogs are vaccinated or tested for immunity． Vaccine will take up t0 2 weeks to reach effective levels of immunity，the contagious individual should remain in quarantine until other animals are protected． Treatment Survival rate depends on how quickly CPV is diagnosed，the age of the animal and how aggressive the treatment is．Treatment for severe cases that are not caught early usually involves extensive hospitalization，due to the severe dehydration and damage to the intestines and中国宠物医师网T5mj,[ dRi b[ ^-d
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_/FiNe0bone marrow．A CPV test should be百Ven as early as possible if CPV is suspected in order to begin early treatment and increase survival rate if the disease is found． Treatment ideally consists of crystalloid IV fluids and／or colloids，antinausea injections(antiemetics) such as metoclopramide，dolasetron，ondansetron and prochlorperazine，and antibiotic injections such as cefoxitin，metronidazole，timentin，or enrofloxacin． 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 such as buprenorphine are also used to counteract the intestinal discomfort caused by frequent bouts of diarrhea． 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 their boay weight，weight changes over time，degree of dehydration at presentation and surface area．The hydration status is originally determined by assessment of clinical factors like tacky mucous membranes，concentration of the urine，sunken eyes，poor skin elasticity and bloodtests． A blood plasma transfusion from a donor dog that has already survived CPV is sometimes used to provide passive immunity to the sick d09．Some veterinarians keep these dogs on site，or have frozen serum available．There have been no controlled studies regarding this treatment． Additionally，flesh frozen plasma and human albumin transfusions can help replace the extreme protein losses seen in severe cases and help assure adequate tissue healin9． 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 patient7s ability to fight off secondary infection．A puppy with minimal symptoms can recover in 2 0r 3 days if the IV fluids are begun as soon as symptoms are noticed and the CPV test confirms the diagnosis． However，even with hospitalization，there is no guarantee that the dog will survive． Unconventional treatments There is no specific antiviral treatment for CPV． However，there have been anecdotal reports of oseltamivir(Tamiflu)reducing disease severity and hospitalization time in canine parvovirus infection． The drug may limit the ability of the virus to invade the crypt cells of the small intestine and decrease gastrointestinal bacteria colonization and toxin production．There is also anecdotal evidence suggesting that colloidal silver is effective at treating CPV although currently regulatory authorities are discouraging its use due to potential toxicity issues and lack of demonstrated efficacy． Lastly， recombinant feline interferon omega (rFelFN一(1))，produced in silkworm larvae using a baculovirus vector，has been demonstrated by multiple studies to be an effective treatment． Prognosis Untreated cases of CPV2 will have a mortality (percentage that will die)approachin9 9 1％．With aggressive therapy survival rates may approach 80-95％8h Pa4y!P9H'^w0
x ?q7Ac$x0犬细小病毒2型(canine parovirus type 2． CPV2)是主要感染犬的一个传染性病毒。该病 的传染性强，可以通过犬间直接接触传播或者 与患犬的粪便间接接触传播。若幼犬没有母源 抗体的保护或者没有进行免疫接种，则会出现 尤为严重的临床症状。该病有2个不同的类型： 心肌炎型和肠炎型。肠炎型患犬的一般症状为 剧烈呕吐和严重的血便。心肌炎型可以导致幼 犬的呼吸系统或心血管系统损伤。该病通常需 要住院治疗。疫苗能有效防止感染，但是，没有 进行治疗的患犬，其致死率高达91％。中国宠物医师网0Y u W8l Q4ue
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犬细小病毒有2种类型：CPVl和CPV2。中国宠物医师网s!t2O:dw9S
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CPV2能引发最为严重的疾病，感染家养犬和野 生犬科动物。CPV2又分为几种类型：CPV一2a、 CPV-2b和CPV一2c。CPV一2a和2b在毒力和 对猫的感染力上与最初的CPV2不同。CPV一2c 是近来发现的与2b相似的一种类型。2c的病毒 蛋白有一个氨基酸与CPV一2b存在差异，这一 点非常重要。2c已经在欧洲、美洲和亚洲分离出 来，正是这个亚型的出现导致了免疫犬发病。但 是，研究证明，目前的CPV疫苗足以提供对 CPV一2c的免疫保护力。中国宠物医师网2Cm$F%s#n Ue
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C5j1X0一、研究历程 在20世纪70年代末，CPV2感染是一个相 对较新的疾病。最早于l978年发现，该病在1～2 年后波及全世界范围。该病毒和猫传染性粒细 胞缺乏症病毒(同样也是细小病毒的一种)相 似，同源性达98％，只在病毒囊膜蛋白VP2上有 2个氨基酸存在差异。该病毒和貂肠炎病毒、浣 熊及狐狸细小病毒高度相似。最初认为是猫传 染性粒细胞缺乏症病毒变化为CPV2。尽管这一 点还没有得到证实，但两者之间极强的相似性 令这个理论最为可信。但是，CPV2可能是一些 野生食肉动物的不确定的细小病毒(类似猫细 小病毒，即FPV)的变异体。CPV一2b的一个毒 株(FP84)已经被证实可以导致一小部分家养猫 发病，尽管FPV疫苗看似可以提供有效保护。但 是，CPV2一般不引起猫发病，也只能引起貂和 浣熊的轻微病症，这个病毒几乎只感染犬。中国宠物医师网 t1y n[n^|R U
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1979年和l984年分别发现了犬细小病毒 CPV一2a和CPV一2b。大多数犬细小病毒感染都 是由这2种毒株引起的，而非最初的毒株，而且 这2种毒株与最初的毒株不同，虽然通过日常 的检测无法区分开来。第三种类型，即CPV一2c， 已经在意大利、越南和西班牙被发现。中国宠物医师网%I!\@ ~D'~sy%D.u&f
;v F\;O0[nh _[X7W0二、病毒学 CPV2是一个无囊膜的单股DNA病毒。名 字起源于拉丁文“parvus”，意思是“小”，病毒的 直径只有20～26nm。病毒粒子呈二十面体对称。中国宠物医师网e
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xc.eG)Q I;E0基因组大约有5000个核苷酸。CPV2不断进化， 新毒株的出现看似依赖宿主范围的扩大和结合 受体的改进，即犬转铁蛋白受体的改进。CPV2 的进化率高，可能是由于核苷酸存在一定的置 换率，这一点和RNA病毒中的流感病毒A相 似。不同的是，FPV看似只能通过随意的基因漂 移进行进化。 Bw p| f$V7r0
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CPV2感染犬、狼、狐狸和其他犬科动物。中国宠物医师网,Za G6^+bv-B OT
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CPV一2a和CPV一2b已经从一小部分出现临床 症状的猫体内分离出来，在大型猫中，比猫传染 性粒细胞缺乏症病毒更为常见。中国宠物医师网 t{6X3h0kpI5Y
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最初认为病毒没有经历过种间感染。然而， 在越南的研究提示，CPV2能经历与感染猫科动z(hOt)n3q0
x y]y/aGQ5?1h@0物不同的细微的抗原漂移和自然突变。对越南 和台湾地区猫细小病毒(FPV)的分析提示，80％ 以上的分离株都属于犬细小病毒，而不是猫传 染性粒细胞缺乏症病毒(FPLV)。CPV2可能传 染给猫比传染给犬更为容易，而且经历更为迅 速的突变。该病毒不能传染鸟或人，但是，当鸟 接触到粪便，然后接触到犬的生活环境，或者当 猫的毛发上携带病毒，然后又回到暴露的宠物 窝里的时候，就能传播病毒。中国宠物医师网 b#G4f
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rC6M7L!M p(J0（—）变异体 CPV2有几种变异体，即cPv一2a、cPv一2b 和CPV一2c。2a和2b的抗原性与最初的CPV2 极为相似。但是，2c的抗原性独特。这一点导致 出现犬免疫的无效性理论，但是，研究证明，现 有的针对2b的CPV疫苗可以提供对2c的有 效保护。然而，有报道提到过去的针对CPV2的 疫苗可能无法提供对2c的有效的交叉保护。
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X!KA yF C${0三、病理生理学 CPV2有2种类型：肠炎型和心肌炎型。幼 犬对病毒极为易感，但是超过80％的成年犬不 表现出任何临床症状。发生严重疾病的患犬，若 没有进行输液治疗和抗生素治疗，在48-72小 时内就会发生死亡。在更为通常的情况下，发生 非严重疾病的患犬，致死率大约为10％。一些品 种的犬，如罗威纳犬、杜宾犬、比特犬和黑色与 黄褐色的犬更易感CPV2。除了年龄和品种外， 其他一些因素，如存在应激的环境、同时感染细 菌和寄生虫以及犬冠状病毒都能增加犬发生严 重感染的几率。细小病毒患犬通常死于疾病引 发的脱水或者非病毒本身引起的继发感染。中国宠物医师网_q%Y2X#g.nd n
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QE-ri` i0（—）肠炎型 犬通过口腔接触到CPV2污染的粪便、感 染的土壤或者携带病毒的污染物而发生感染。中国宠物医师网XAJAkL+ty
s2k5gN4bW'C_K0通过消化，病毒在咽部淋巴结中进行增殖，然后 扩散到血液中。从这个时候开始，病毒开始迅速 攻击分裂细胞，尤其是淋巴结、肠腺和骨髓的细 胞。淋巴结中的淋巴细胞数量剧减、发生坏死， 肠腺被破坏。平时生活在肠道内的厌氧菌进入 血液中，这个过程就是所谓的位置转移，导致发 生败血症。严重病例中最为常见的细菌包括梭 状芽胞杆菌、弯曲杆菌属和沙门氏菌属。这能导 致所谓的全身炎症反应综合征(sIRs)。SIRS导 致一些病症，如血液高凝结状态、内毒素血症和 急性呼吸窘迫综合征(ARDS)。有败血症发生后 出现细菌性心肌炎的报道。CPV患犬有肠套叠 的危险，即一段肠管脱出于另一段肠管之上。感 染后的3-4天，患犬能从粪便中持续排毒3周， 也可能没有出现任何临床症状，但在一段时间 内持续向外排毒。当病毒与蠕虫或其他肠道寄 生虫共感染时，通常更加致命。中国宠物医师网.{.X v%OvET7R3I
2V0Y n a xn `\ b0（二）心-肌炎型 这种类型比较少见，感染子宫内或出生后8 周以内的幼犬。病毒攻击心肌，幼犬通常发生突 然死亡或者在一阵呼吸困难后突然死亡。在显 微镜下观察，心肌上有很多坏死点，并存在单核 细胞浸润。在存活下来的患犬中经常发现过多 纤维组织的生成(纤维化)。肌纤维是病毒在细 胞内进行增殖的地方。该病能同时出现或不出 现肠炎型的症状。然而，通过对种犬的广泛免 疫，这种类型已经不常见。中国宠物医师网/R7l)a h e^#Af.D
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尽管不常见，但是该病也可能导致新生幼 犬的广泛性感染，引起胃肠道或者心脏以外的 其他组织的损伤，并在其中进行病毒增殖和攻 击，包括脑、肝脏、肺脏、肾脏和肾上腺皮质。血 管内壁也可能发生严重感染，导致损伤部位发 生出血性病变。(EH1]U&_x
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V nf7X*B|M Q/q)k0（三）子宫内的感染 这种类型的感染发生在怀孕母犬感染 CPV2的时候，母犬可能产生免疫力，只出现轻 微的临床症状或者没有任何临床症状。病毒可 能已经通过胎盘感染胎儿。这能导致一些异常中国宠物医师网8jp+n6q M2tht0a
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情况。严重的时候，胎儿可能石化或者干尸化， 不严重的时候，幼犬可能发生神经异常，如小脑 发育不全。中国宠物医师网Q NT)z` X*[W,_
\X.X'uF/S(D1y0四、临床症状 犬在感染病毒5～10天后表现出临床症状。中国宠物医师网9I1y,a5y7@!c k;p
%a` ZUW#|9n8Q?1n;{7y0精神不振、呕吐、发热和腹泻(通常便血)。腹泻 和呕吐导致机体发生脱水和继发感染。因为脱 水，患犬的电解质平衡受到严重影响。由于正常 的肠壁免疫力受到影响，血液和蛋白渗透到肠 道内，导致机体发生贫血和蛋白质丢失，内毒素 也进入血流中，导致内毒素血症。患犬在感染后 期有特殊气味。白细胞总数下降，患犬更加虚 弱。以上任何一个因素或所有因素均能导致患 犬发生休克和死亡。中国宠物医师网|j X.NfWv*l
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五、诊断 通过电免疫分析、血凝试验或者电镜检查 粪便中的CPV2，均能对该病做出诊断。目前已 经可以通过PCR诊断CPV2，而且当通过电免 疫分析不能检查到粪便中的微量病毒时，PCR 仍然可以应用。临床上，肠炎型的患犬有时和冠 状病毒感染或其他类型的肠炎混淆。然而，细小 病毒感染更为严重，而且便血性腹泻、白细胞总 数降低和肠道内壁坏死都能提示细小病毒的存 在，特别是未经免疫的犬。心肌炎型的患犬容易 诊断，因为其临床症状比较特殊。中国宠物医师网 ~CD JE*E3W
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六、预防和净化 当疾病处于毒力旺盛和传染性极强的时 候，只有通过预防措施，才能保证幼犬或犬的健 康状态。病毒生命力相当顽强，能在粪便或有机 物质如土壤中生存一年之久。在极低的温度或 高温中也能存活。家中唯一能消灭病毒的消毒 剂就是次氯酸钙溶液。N|8ga
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3~"`T8z/PNpA tAi0断奶幼犬可以免疫接种改良的低传代次 数、高滴度的病毒疫苗，免疫时间为6周龄，以 后每隔3～4周免疫1次，直到l5～16周为止。幼 犬在最初的时候能够从母犬体内获得被动免疫 力。这些母源抗体在幼犬免疫系统成熟之前足 以抵抗CPV2感染。母源抗体也能干扰CPV2 疫苗，导致免疫失败。因此，幼犬通常需要分时 间段进行免疫接种，从母源抗体开始减弱直到 被动免疫彻底消失。大一点的幼犬(16周龄或者 更大)都在不同时间段进行了3～4次免疫。对美 国所有大型生产商的疫苗进行了疫苗保护时间 的检测，结果表明，若进行了最初的几次免疫接 种和一年之后的一次加强免疫，则保护时间至 少能达3年。gUBRC/P:K0
Xc3j&w;g'r/r)Q0CPV2患犬顺利康复后能持续几天从粪便 中排出病毒。因为病毒能在环境中存活数月，所 以，环境中的粪便污染是持续性感染的重要威 胁。邻居或者养犬的家庭成员应知晓感染动物 以确保自己的犬能进行免疫，或者进行检查。疫 苗需要在接种2周后才能达到有效的免疫保护 水平，所以，感染的个体仍然需要隔离，以确保 其他动物的安全。中国宠物医师网7~6JA(}
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{-j]5QHE x]d {0七、治疗 患犬的存活率依赖CPV的诊断时间、患犬 的年龄和治疗方法的有效性。对没有及时诊断 出来的严重病例，通常会延长住院时间，因为机 体脱水严重，并且肠道和骨髓都有损伤。为了尽 早进行治疗，提高存活率，若怀疑存在CPV感 染，则应该尽早进行CPV检测。7@ o.k!`4FI8D1t+\7bJ0
)r?I.fg:e0理想的治疗包括晶体Iv溶液和／或胶体溶 液，止吐药，如胃复安、多拉司琼、奥坦西隆和普 鲁氯嗪，以及抗生素，如头孢西丁、甲硝唑、特美 汀或者恩氟沙星。Iv溶液通过皮下注射，止吐药 通过肌内注射，抗生素通过静脉滴注。溶液一般 是灭菌、平衡的电解质溶液，同时有一定数量的 复合8族维生素、葡萄糖和氯化钾。止痛药，如 丁丙诺啡，也用于缓解因多次腹泻导致的肠道 异常。&d)`#A_t3{2B5^8P0
fOw'K E~Q0此外，为确保输入液体能充分缓解脱水状 态，当幼犬发生严重呕吐或者腹泻之后，要应用 等量的液体进行静脉滴注。液体的需要量取决 于患犬的体重、不同时间段的体重变化以及表 象和表面的脱水程度。脱水程度最初是根据临 床表现如粘膜、尿液浓度、下陷的眼眶、皮肤弹 性较差以及血液学检验来判断的。中国宠物医师网%thY QNU&Hg
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通过向患犬体内输入曾患CPV的康复犬 的血浆，有时能够为患犬提供被动免疫保护力。中国宠物医师网`a1d&Y1G{
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一些宠物医师饲养这些康复犬，或者把康复犬 的血清冷冻。但是迄今还没有关于这种治疗方 法的严格的研究。此外，输入新鲜的冷冻血浆和 人白蛋白能够帮助患犬恢复大量丢失的蛋白 质，保证组织充分愈合。~o!eZ
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)d jV(P9y,\0~0一旦患犬的体液开始稳定，就可以不再使 用Iv液体，并慢慢给予患犬一些无刺激性的食 物。根据患犬白细胞总数和抵抗继发感染能力 的情况，让患犬口服抗生素几天。若一旦发现症 状即给予Iv液体，并且通过CPV检查进行了 确诊，那么，出现轻微症状的幼犬能在2～3天内 康复。然而，即使入院治疗，也不能保证患犬一 定能存活下来。中国宠物医师网'}3XF C d
.j9D(o'q6\ps p0非传统疗法 CPV没有特殊的抗病毒疗法，然而，有一个 有趣的报道提到奥塞米韦能减轻疾病的严重性 和减少住院时间。该药能限制病毒入侵小肠的 滤泡细胞，减少胃肠道细菌滋生和毒素产生。还 有一个有趣的报道提到胶态微粒银能有效治疗 CPV，尽管目前管理当局不推荐使用该药，因为 它对组织有潜在的毒性，并且没有确切的药效。中国宠物医师网N+UK,TcE
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最后，利用杆状病毒属蚕幼虫制备的重组猫干 扰素一(I)已经被证实对CPV的治疗有效。^MNO0b!~R{0
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f0八、预后 没有进行治疗的CPV2患犬的死亡率高达 91％，而进行积极治疗的患犬的存活率可能达到 80％～95％。 n7NBJE"Pe0
