宠物犬和猫流感病毒感染

近十年来犬和猫流感病毒感染报道迅速增多,不仅威胁到犬和猫的健康,也对公共卫生造成了影响。自2004年首次发生H3N8亚型流感病毒感染赛犬事件以来,犬流感一直在美国的赛犬和宠物犬中流行。在韩国和我国南方的犬群中出现了因H3N2亚型禽流感感染引起的肺炎病例。亚洲和欧洲均报道了猫H5N1亚型高致病性禽流感致死性感染病例,还通过实验研究发现H5N1亚型流感病毒可在猫与猫之间水平传播。这些现象预示着流感病毒进一步获得了感染哺乳动物的能力,其公共卫生意义需引起关注。为此,本文对犬和猫流感病毒感染的流行病学、临床症状、发病机制、诊断和防控措施进行了综述。     

Experimental Infections of Dogs with Type C Influenza Virus

A study was performed to determine if type C influenza infection could be established in dogs as a model for human cases. Mongrel dogs were infected with the Ann Arbor/1/50 strain of type C influenza virus and were examined for clinical symptoms, virus isolation and antibody response. After the first exposure to the virus, all infected animals developed nasal discharge and some of them also showed swelling of the eyelids, and suffusion of the eyes with tears and eye mucus, within 1 to 4 days. The animals showed an increase in hemagglutination-inhibiting (HI) serum antibody, and recovery of the agent from the nasal swabs was successful. The symptoms lasted for as long as 10 days in most infected dogs, which was comparable to our human cases reported previously (Katagiri, S., Ohizumi, A., and Homma, M. 1983. J. Infect. Dis. 48 : 51–56). After the second and third virus exposures at intervals of 50 days, all animals developed the same symptoms as those described above and the rise in antibody titer was evident. The virus could be recovered from four of the six dogs 2 to 5 days after the second exposure and from one dog as late as 10 days after the third exposure. Increases in antibody titer in the IgM fraction were observed after every infection. In control dogs which were mock-infected with UV-inactivated virus, no symptoms were evident and recovery of the virus was not successful although an increase in HI serum antibody titer was seen. These results show that mongrel dogs are sensitive to type C influenza virus and that repeated infections characteristic of human influenza C can be experimentally produced in dogs.     

Intermediate Hosts of Angiostrongylus cantonensis in Tenerife,Spain

The nematode Angiostrongylus cantonensis is the causative agent of human angiostrongyliasis, the main clinical manifestation of which is eosinophilic meningitis. Although this parasite has been found recently in its definitive rat host in Tenerife (Canary Islands, Spain), showing a widespread distribution over the north-east part of the island, there are no available data regarding which snail and/or slug species are acting as intermediate hosts on this island. Consequently, the objective of this work was to determine the possible role of three mollusc species, Plutonia lamarckii, Cornu aspersum and Theba pisana, as intermediate hosts of A. cantonensis in Tenerife. Between 2011 and 2014, 233 molluscs were collected from five biotopes where rats had been found previously to harbor either adult worms or antibodies against A. cantonensis, and the identification was carried out on the basis of morphological features and a LAMP technique. The prevalence of A. cantonensis larvae in the mollusc samples, based on morphological identification, was 19.3%, whereas 59 out of the 98 individuals (60.2%) analyzed by LAMP were positive. Positive results were obtained for the three mollusc species analyzed and two of the positive samples, both obtained from P. lamarckii, were confirmed as positive by 18S rRNA and ITS1 PCR. Sequence analysis of 18S rRNA PCR products showed 100% similarity with previously published A. cantonensis sequences. These results may be relevant from a public health point of view, since all the biotopes from which the samples were obtained were in inhabited areas or areas with human activity, but it is also important from the perspective of a possible transmission to other accidental hosts, such as dogs and horses, animals that are present in some of the areas analyzed.     

Passive Immunization against Exposure to Hepatitis B Virus in the Military: Potential and Possibilities

The value of standard γ-globulin with a low titer of antibody to hepatitis B surface antigen (anti-HB_s) vs hepatitis B immune globulin (HBIG) in prevention of icteric hepatitis B in the military is unclear. Although recent studies have shown a decrease in icteric hepatitis after administration of both types of γ-globulin in populations where acquisition of hepatitis B virus (HBV) is most likely the result of nonparenteral transmission, the data pertaining to parenteral exposure suggest that HBIG delays the incubation period of HBV and decreases the development of passive-active immunity. Since no studies have demonstrated efficacy of standard γ-globulin or HBIG in a drug-using population where multiple HBV exposures are likely, the results observed in most trials are not comparable to hepatitis B associated with drug abuse in the military. Therefore, before a recommendation for use of routine γ-globulin or HBIG can be made for drug-related hepatitis in the military, efficacy of standard γ-globulin and/or HBIG should be demonstrated in this population.     

The Role of Birds as Definitive Hosts and Intermediate Hosts of Heteroxenous Coccidians

ABSTRACT. Sarcocystis- like oocysts-sporocysts were found in four species of owls (Asio otus, Bubo bubo, Strix aluco , and Tyto alba) and in five species of predatory birds (Accipiter gentilis, Accipiter nisus, Buteo buteo. Circus aeruginosus, Falco tinnunculus). In addition, the muscles of 15 of 41 (36.5%) pheasants (Phasianus colchicus) and one of two jays (Garrulus glandarius) were found to harbor three types of Sarcocystis. Three of 15 (20%) infected pheasants had type I cystozoites (6-8 × 2 fim) in muscle homogenates, but sarcocysts were not seen whereas the other 12 infected pheasants had type II cystozoites (16 × 2-3 pm) and sarcocysts (90 × 600 μm) in their muscles. The one infected jay had type III cystozoites (8-10.5 × 2.5-3 μm) and sarcocysts (35-40 × >770 μm) in its muscles.     

Vectors,Hosts, and Control Measures for Zika Virus in the Americas

We examine Zika virus (ZIKV) from an ecological perspective and with a focus on the Americas. We assess (1) the role of wildlife in ZIKV disease ecology, (2) how mosquito behavior and biology influence disease dynamics, and (3) how nontarget species and ecosystems may be impacted by vector control programs. Our review suggests that free-ranging, non-human primates may be involved in ZIKV transmission in the Old World; however, other wildlife species likely play a limited role in maintaining or transmitting ZIKV. In the Americas, a zoonotic cycle has not yet been definitively established. Understanding behaviors and habitat tolerances of Aedes aegypti and Aedes albopictus, two ZIKV competent vectors in the Americas, will allow more accurate modeling of disease spread and facilitate targeted and effective control efforts. Vector control efforts may have direct and indirect impacts to wildlife, particularly invertebrate feeding species; however, strategies could be implemented to limit detrimental ecological effects.     

Selection of H5N1 Influenza Virus PB2 during Replication in Humans

Highly pathogenic H5N1 influenza viruses continue to cause concern, even though currently circulating strains are not efficiently transmitted among humans. For efficient transmission, amino acid changes in viral proteins may be required. Here, we examined the amino acids at positions 627 and 701 of the PB2 protein. A direct analysis of the viral RNAs of H5N1 viruses in patients revealed that these amino acids contribute to efficient virus propagation in the human upper respiratory tract. Viruses grown in culture or eggs did not always reflect those in patients. These results emphasize the importance of the direct analysis of original specimens.Given the continued circulation of highly pathogenic H5N1 avian influenza viruses and their sporadic transmission to humans, the threat of a pandemic persists. However, for H5N1 influenza viruses to be efficiently transmitted among humans, amino acid substitutions in the avian viral proteins may be necessary.Two positions in the PB2 protein affect the growth of influenza viruses in mammalian cells (3, 11, 18): the amino acid at position 627 (PB2-627), which in most human influenza viruses is lysine (PB2-627Lys) and most avian viruses is glutamic acid (PB2-627Glu), and the amino acid at position 701. PB2-627Lys is associated with the efficient replication (16) and high virulence (5) of H5N1 viruses in mice. Moreover, an H7N7 avian virus isolated from a fatal human case of pneumonia possessed PB2-627Lys, whereas isolates from a nonfatal human case of conjunctivitis and from chickens during the same outbreak possessed PB2-627Glu (2).The amino acid at position 701 in PB2 is important for the high pathogenicity of H5N1 viruses in mice (11). Most avian influenza viruses possess aspartic acid at this position (PB2-701Asp); however, A/duck/Guangxi/35/2001 (H5N1), which is highly virulent in mice (11), possesses asparagine at this position (PB2-701Asn). PB2-701Asn is also found in equine (4) and swine (15) viruses, as well as some H5N1 human isolates (7, 9). Thus, both amino acids appear to be markers for the adaptation of H5N1 viruses in humans (1, 3, 17).Massin et al. (13) reported that the amino acid at PB2-627 affects viral RNA replication in cultured cells at low temperatures. Recently, we demonstrated that viruses, including those of the H5N1 subtype, with PB2-627Lys (human type) grow better at low temperatures in cultured cells than those with PB2-627Glu (avian type) (6). This association between the PB2 amino acid and temperature-dependent growth correlates with the body temperatures of hosts; the human upper respiratory tract is at a lower temperature (around 33°C) than the lower respiratory tract (around 37°C) and the avian intestine, where avian influenza viruses usually replicate (around 41°C). The ability to replicate at low temperatures may be crucial for viral spread among humans via sneezing and coughing by being able to grow in the upper respiratory organs. Therefore, the Glu-to-Lys mutation in PB2-627 is an important step for H5N1 viruses to develop pandemic potential.However, there is no direct evidence that the substitutions of PB2-627Glu with PB2-627Lys and PB2-701Asp with PB2-701Asn occur during the replication of H5N1 avian influenza viruses in human respiratory organs. Therefore, here, we directly analyzed the nucleotide sequences of viral genes from several original specimens collected from patients infected with H5N1 viruses.     

Complete Genome Sequence of an H3N2 Canine Influenza Virus from Dogs in Jiangsu,China

A canine influenza virus (CIV) strain of avian origin designated A/Canine/Jiangsu/06/2010 (H3N2) was isolated from dogs exhibiting severe respiratory disease in Jiangsu, China. We announce the complete genome sequence of this viral strain and report major findings from the genomic analysis. This sequence will help us understand the molecular characteristics and evolutionary of H3N2 CIV in China.     

禽流感病毒新型疫苗的研究进展

疫苗免疫是禽流感防控的主要措施之一,随着生物技术的不断发展,基因工程亚单位疫苗、活载体疫苗、DNA疫苗等新型疫苗得以研究和开发,这为禽流感的防控提供了新的手段。新型疫苗除具有传统疫苗的保护效果外,在生物安全和普遍防控等方面也具有广泛的优势,是禽流感疫苗发展的新方向。     

禽流感病毒跨种属感染人的机制研究进展

禽流感病毒(avian influenza virus,简称AIV)不仅引起禽类感染和流行,而且可以打破种属屏障(speciesbarrier)、引起人或其他哺乳动物感染和传播。近年来对人呼吸道抗禽流感病毒感染的非特异屏障机制、禽流感病毒对人感染的机制研究不断取得新的进展。     

Echinostoma revolutum: Freshwater Snails as the Second Intermediate Hosts in Chiang Mai,Thailand

The occurrence of 37-collar spined echinostome metacercariae in freshwater snails was investigated in 6 districts of Chiang Mai Province, Thailand, from October 2011 to April 2012. A total of 2,914 snails that belong to 12 species were examined, and 7 snail species (Clea helena, Eyriesia eyriesi, Bithynia funiculata, Bithynia siamensis siamensis, Filopaludina doliaris, Filopaludina sumatrensis polygramma, and Filopaludina martensi martensi) were found infected with echinostome metacercariae. The prevalence of metacercariae was the highest in Filopaludina spp. (38.5-58.7%) followed by B. funiculata (44.0%), E. eyriesi (12.5%), B. siamensis siamensis (8.2%), and C. helena (5.1%). Metacercariae were experimentally fed to hamsters and domestic chicks, and adult flukes were recovered from both hosts at days 15 and 20 post-infection. The adult flukes were identified based on morphological features, morphometrics, host-parasite relationships, and geographical distribution. They were compatible to Echinostoma revolutum or Echinostoma jurini, with only minor differences. As the adults were recovered from both hamsters and chicks, our specimens were more compatible to E. revolutum rather than E. jurini (reported only from mammals). This is the first report for metacercariae of E. revolutum in the snail host, C. helena, and also confirmed that Filopaludina spp., E. eryresi, and Bithynia spp. act as the second intermediate hosts of E. revolutum under natural conditions, which are indigenously distributed in Chiang Mai province.     

Plasminogen Activator Inhibitor-1 in Cigarette Smoke Exposure and Influenza A Virus Infection-Induced Lung Injury

Parenchymal lung inflammation and airway and alveolar epithelial cell apoptosis are associated with cigarette smoke exposure (CSE), which contributes to chronic obstructive pulmonary disease (COPD). Epidemiological studies indicate that people exposed to chronic cigarette smoke with or without COPD are more susceptible to influenza A virus (IAV) infection. We found increased p53, PAI-1 and apoptosis in AECs, with accumulation of macrophages and neutrophils in the lungs of patients with COPD. In Wild-type (WT) mice with passive CSE (PCSE), p53 and PAI-1 expression and apoptosis were increased in AECs as was lung inflammation, while those lacking p53 or PAI-1 resisted AEC apoptosis and lung inflammation. Further, inhibition of p53-mediated induction of PAI-1 by treatment of WT mice with caveolin-1 scaffolding domain peptide (CSP) reduced PCSE-induced lung inflammation and reversed PCSE-induced suppression of eosinophil-associated RNase1 (EAR1). Competitive inhibition of the p53-PAI-1 mRNA interaction by expressing p53-binding 3’UTR sequences of PAI-1 mRNA likewise suppressed CS-induced PAI-1 and AEC apoptosis and restored EAR1 expression. Consistent with PCSE-induced lung injury, IAV infection increased p53, PAI-1 and apoptosis in AECs in association with pulmonary inflammation. Lung inflammation induced by PCSE was worsened by subsequent exposure to IAV. Mice lacking PAI-1 that were exposed to IAV showed minimal viral burden based on M2 antigen and hemagglutination analyses, whereas transgenic mice that overexpress PAI-1 without PCSE showed increased M2 antigen and inflammation after IAV infection. These observations indicate that increased PAI-1 expression promotes AEC apoptosis and exacerbates lung inflammation induced by IAV following PCSE.     

Molecular Investigations of Rickettsia helvetica Infection in Dogs,Foxes, Humans,and Ixodes Ticks

Rickettsia helvetica, a tick-borne member of the spotted-fever-group rickettsiae, is a suspected pathogen in humans; however, its role in animals is unknown. The aims of this study were to establish a R. helvetica-specific real-time TaqMan PCR assay and apply it to the analysis of tick vectors (to determine potential exposure risk) and blood samples from Canidae and humans (to determine prevalence of infection). The newly designed 23S rRNA gene assay for R. helvetica was more sensitive than a published citrate synthase gene (gltA) assay for several rickettsiae. Blood samples from 884 dogs, 58 foxes, and 214 human patients and 2,073 ticks (Ixodes spp.) collected from either vegetation or animals were analyzed. Although the maximal likelihood estimate of prevalence was 12% in unfed ticks and 36% in ticks collected from animals, none of the 1,156 blood samples tested PCR positive. Ticks from cats were more frequently PCR positive than ticks from dogs. Sequencing of the 23S rRNA and/or the gltA gene of 17 tick pools confirmed the presence of R. helvetica. Additionally, Rickettsia monacensis, which has not been previously found in Switzerland, was identified. In conclusion, R. helvetica was frequently detected in the tick population but not in blood samples. Nevertheless, due to the broad host range of Ixodes ticks and the high rate of infestation with this agent (i.e., R. helvetica was 13 times more frequent in unfed ticks than the tick-borne encephalitis virus), many mammals may be exposed to R. helvetica. The PCR assay described here represents an important tool for studying this topic.Tick-borne rickettsioses are caused by intracellular bacteria belonging to the spotted fever group (SFG) of the genus Rickettsia. The latter comprises more than 20 different species, of which an increasing number are known to be associated with human and animal diseases. The SFG rickettsiae are distributed worldwide, and their distribution depends upon the occurrence of tick species. The most common tick in Europe is Ixodes ricinus, which was found to harbor Rickettsia helvetica. R. helvetica is transmitted not only transstadially but also transovarially in I. ricinus. Therefore, this tick is both a vector and a reservoir for R. helvetica. Due to the broad host range of I. ricinus, many mammalian species, including humans, can serve as hosts. Therefore, these host species may potentially be exposed to R. helvetica. R. helvetica is a suspected pathogen in humans, and the symptoms described for infections in humans include fever, headache, arthralgia, and myalgia (1, 3, 7, 21, 34). The agent also has been implicated in two cases of fatal perimyocarditis (20, 22).Interestingly, despite the wide distribution of I. ricinus ticks and the high rate of infection of these ticks with R. helvetica that has been reported in several European countries (2, 9, 18, 19, 25, 29, 35, 42), larger studies discussing the prevalence of the infection in humans and animals are scarce. No studies evaluating the importance of R. helvetica in pets or farm animals are available as yet. It is unknown whether these animals can serve as a reservoir or develop clinical signs after infection.Rickettsial infections have been reported to represent the third most common vector-borne disease acquired during international travel and are therefore considered a common cause of fever of unknown origin in returned travelers (24). As the occurrence of tick-borne infectious diseases, and particularly rickettsial infections, is increasing in humans worldwide (26), it may be assumed that the same holds true for companion animals. In dogs, fever of unknown origin that is responsive to antibiotic treatment is frequently observed. In these cases, an infectious agent is suspected but rarely, if ever, confirmed. R. helvetica infections may be the underlying cause in some of these cases, even if the patient does not have a travel history, since exposure to R. helvetica-infected I. ricinus ticks may have occurred locally.To date, the diagnosis of rickettsial infection has most often been confirmed by serological testing. However, antibodies are not detectable prior to the second week of illness for any rickettsial disease studied thus far. Moreover, except for detection of seroconversion or a fourfold increase in titer, a positive serology result does not necessarily indicate an acute infection. A standardized sensitive and specific molecular method for the confirmation of R. helvetica infections would facilitate not only its diagnosis but also prevalence studies. This in turn could increase the awareness of physicians and veterinarians who are confronted with diseased individuals.Therefore, the aims of the present study were as follows: first, to establish a sensitive real-time PCR assay specific for R. helvetica; second, to study tick vectors for R. helvetica to assess the potential exposure risk for animals and humans; and third, to evaluate blood samples from Canidae and humans to assess the occurrence of R. helvetica infections.(These studies were conducted by A. Perreten as partial fulfillment of the requirements for a doctoral thesis at the Vetsuisse Faculty, University of Zurich.)