The identification of new virus species is a key issue for the study of infectious disease but is technically very difficult. We developed a system for large-scale molecular virus screening of clinical samples based on host DNA depletion, random PCR amplification, large-scale sequencing, and bioinformatics. The technology was applied to pooled human respiratory tract samples. The first experiments detected seven human virus species without the use of any specific reagent. Among the detected viruses were one coronavirus and one parvovirus, both of which were at that time uncharacterized. The parvovirus, provisionally named human bocavirus, was in a retrospective clinical study detected in 17 additional patients and associated with lower respiratory tract infections in children. The molecular virus screening procedure provides a general culture-independent solution to the problem of detecting unknown virus species in single or pooled samples. We suggest that a systematic exploration of the viruses that infect humans, “the human virome,” can be initiated.

https://www.pnas.org/content/pnas/102/36/12891.full.pdf

Cloning of a human parvovirus by molecular screening of respiratory tract samples

Rodents are the most abundant and diversified order of living mammals in the world. Already since the Middle Ages we know that they can contribute to human disease, as black rats were associated with distribution of plague. However, also in modern times rodents form a threat for public health. In this review article a large number of pathogens that are directly or indirectly transmitted by rodents are described. Moreover, a simplified rodent disease model is discussed.

Rodent-borne diseases and their risks for public health

Infection of cattle with bovine viral diarrhea virus (BVDV) occurs frequently. The outcome of BVDV infection is a wide range of clinical manifestations. The form of clinical disease observed depends on the agent, host, and environmental factors, as well as interaction of these factors. The clinical manifestations are reviewed in terms of BVDV infection in animals that are immuno-competent to BVDV, fetal infections, and cattle that are immuno-tolerant to BVDV.

The clinical manifestations of bovine viral diarrhea infection.

Background. Human bocavirus is a newly discovered parvovirus. It has been detected primarily in children with acute lower respiratory tract infection, but its occurrence, clinical profile, and role as a causative agent of respiratory tract disease are not clear. Methods. We investigated the presence of human bocavirus by quantitative polymerase chain reaction of nasopharyngeal aspirate specimens and selected serum samples obtained from 259 children (median age, 1.6 years) who had been hospitalized for acute expiratory wheezing. The samples were analyzed for 16 respiratory viruses by polymerase chain reaction, virus culture, antigen detection, and serological assays. Results. At least 1 potential etiologic agent was detected in 95% of children, and >1 agent was detected in 34% of children. Human bocavirus was detected in 49 children (19%). A large proportion of the cases were mixed infections with other viruses, but human bocavirus was the only virus detected in 12 children (5%). High viral loads of human bocavirus were noted mainly in the absence of other viral agents, suggesting a causative role for acute wheezing. In addition, infections that had uncertain clinical relevance and low viral loads were prevalent. Human bocavirus DNA was frequently detected in serum specimens obtained from patients with acute wheezing, suggesting systemic infection. Conclusions. Human bocavirus is prevalent among children with acute wheezing and can cause systemic infection. Results suggest a model for bocavirus infection in which high viral loads are potentially associated with respiratory symptoms and low viral loads indicate asymptomatic shedding. Therefore, quantitative polymerase chain reaction analysis may be important for additional studies of human bocavirus.

Human bocavirus and acute wheezing in children.

Two isolates of canine parvovirus (CPV) were obtained from dogs affected with severe haemorrhagic diarrhoea. Type 2b antigenic specificity was predicted by both antigenic analysis with monoclonal antibodies and PCR characterization with type-specific primers. Nevertheless, sequence analysis of the capsid protein-encoding gene revealed two amino acid changes. One of the changes affected position 426 (Asp to Glu), in a major antigenic site of the viral capsid, determining the replacement of a residue unique to CPV type 2b. The failure of established typing methods to distinguish this antigenic variant was overcome by the development of an RFLP assay.

Evidence for evolution of canine parvovirus type 2 in Italy

Differences in the pathogenesis of porcine parvovirus (PPV) were shown when pregnant gilts were infected by the oral and intramuscular (i.m.) routes.

Observations on the pathogenesis of porcine parvovirus infection

Basic variables of the haemagglutination inhibition (HI) test for porcine parvovirus antibody were investigated. Nonspecific serum inhibitors were satisfactorily removed without loss of specific antibody when undiluted serum was adsorbed with 25 percent kaolin in borate saline at pH 9.0. Natural haemagglutinins in test serums could be completely removed using 0.1 ml of packed erythrocytes to 0.6 ml of kaolin treated serums. Adsorption of prediluted serum resulted in a depression of specific antibody titres. Highest HI titres were obtained using guinea pig erythrocytes, following incubation of virus-serum mixtures for 18 hours at 4 degrees C, 3 hours at 25 degrees C or 2 hours at 37 degrees C. Micro- and macro-tests gave comparable HI titres.

A standardised haemagglutination inhibition test for porcine parvovirus antibody.

Isolation from dogs with severe enteritis of a parvovirus related to feline panleucopaenia virus

Association of bovine viral diarrhoea-mucosal disease virus with ovaritis in cattle.

Summary
Evidence presented suggests that porcine parvovirus is highly stable and infective. Introduction of virus to susceptible herds results in 100% infection rate within the following 3 months. Active immunity is associated with high persistent levels of haemagglutination-inhibitating (HI) antibody (> 256), piglets suckling immune sows acquiring HI titres between 10,000 and 40,000. Loss of passive immunity, measured by HI, occurs in a majority of pigs between 14 and 26 weeks of age (mean 21 weeks), whilst an average of 25% (2–47%) of pigs lose HI titres between 26 and 36 weeks of age. Susceptibility to challenge with virus does not occur until 3–5 weeks following loss of HI titres. In endemically infected herds 98–100% of adult pigs show serological evidence of active immunity.

A significant proportion of gilts may not be actively immune to porcine parvovirus at the time of first service, and subsequent infection may occur while these gilts are pregnant.

R. H. Johnson

Papers

Observations on the pathogenesis of porcine parvovirus infection

A standardised haemagglutination inhibition test for porcine parvovirus antibody.

Isolation from dogs with severe enteritis of a parvovirus related to feline panleucopaenia virus

Association of bovine viral diarrhoea-mucosal disease virus with ovaritis in cattle.

Observations on the epidemiology of porcine parvovirus