Porcine bocavirus (PBoV) is a newly identified parvovirus belonging to the family Parvoviridae, within Parvovirinae subfamily and Bocavirus genus.1 Similar to other bocaviruses, PBoV contains single-stranded, 4- to 6- kb long, autonomously replicating DNA genome with terminal palindromic sequences. The virus genome contains 4 open-reading frames.2
PBoV was first described in the lymph nodes of Swedish swine herds with postweaning multisystemic wasting syndrome in 2009 using random amplification and large-scale sequencing techniques.3 After its identification, the virus has been detected in swine suffering from respiratory and intestinal diseases in addition to asymptomatic swine worldwide.4 It has been found that the virus may also cause reproductive complications.5 PBoV has been isolated from various samples including stool, serum, lymph nodes, tonsils, liver and urine of infected pigs.6
Based on our knowledge, the importance of this virus has been discussed in veterinary medicine, and to date, there have been no reports on the isolation of this virus from humans. Here, we report the first identification of PBoV in a child with symptoms of respiratory tract infection in northeastern Iran.
A 3-year-old child was brought to pediatric clinic of a university hospital in Bojnurd, northeastern Iran, with the chief complaint of cough. According to his parents, he had dry cough for 3 days accompanied by rhinorrhea, low-grade fever and decreased appetite for 2 days. He had no history of any major diseases.
On physical examination, heart rate of 100/min, respiratory rate of 28/min, blood pressure of 90/60 mm Hg and axillary temperature of 37.8°C were recorded. Moreover, mild erythema in the throat without exudate lymphadenopathy and clear rhinorrhea was observed. Lung examination was normal without crackles or whizzing. Moreover, there was no evidence of bronchitis, respiratory distress and pneumonia. In addition, we found no signs of chills, severe fatigue, malaise, tachypnea, tachycardia, cyanosis or loss of consciousness. The patient was diagnosed with upper respiratory tract infection by the pediatric physician and given normal saline nasal drops, herbal syrup for cough and acetaminophen for his fever, and the patient was discharged. The patient was included in a health surveillance project on the viral causes of upper respiratory tract infection with the parents’ permission, and a nasopharyngeal swab was taken and frozen. The patient was followed up after 5 days, and his mother stated that the symptoms had resolved.
Carrying out a large project on human bocavirus (HBoV) detection in children with upper respiratory infection, we extracted and analyzed DNA for HBoV by polymerase chain reaction using the common primer pair for targeting the Nucleoprotein 1 (NP1) region of the HBoV genome. The positive samples were further analyzed with sequence analysis. National Center for Biotechnology Information (NCBI) blast program showed more than 89% homology with PBoV 1pig/ZJD/China/2006 sequence, accession number HM053693.2.
The results were negative for other respiratory viruses including human metapneumovirus, adenovirus, rhinovirus, respiratory syncytial virus, enterovirus, influenza virus, parainfluenza virus and human coronavirus. Further interview with the parents suggested possible contact with pigs’ secretions because of their rural residence and proximity of wild boars while commuting to their farm.
Bocaviruses have been recognized in humans, canines, cattle, cats, gorillas and seals. PBoV, a newly discovered parvovirus in the family Parvoviridae, seems to be widely spread among swine herds worldwide.7 After its discovery in 2009, several different strains of PBoV have been reported from various regions such as North America, Asia, the United Kingdom, Eastern Europe and Africa.5 But likely to date no cases have been reported in Iran.
In this study, because there were no other respiratory viruses and based on the sequence homology to PBoV, it seems likely that PBoV was the cause of the respiratory symptoms in this case. PBoV sequences were coincidentally detected in the nasopharyngeal sample of our patient in a screening project.
PBoVs and human strains are antigenically cross-reactive. Viral recombination has also been documented in both human and porcine BoVs, and the possibility of cross-species transmission should be considered. At least 4 different HBoV species have been described that cause respiratory and gastrointestinal diseases.8,9 While animal BoVs are relatively distinct from human strains, PBoV seems to share more genetic homology to HBoV than other animal strains based on the NS1 gene.5
Because of close contact between humans and pigs in pork-producing countries, the possibility of human infection with PBoV is possible and requires further study.3
In Iran, because of the Islamic ban on pork consumption, human–pig contact is not likely through pig farming. However, our patient could have been in contact with pigs’ excretions because many wild boars are constantly observed in rural regions or within farms in northeastern Iran. Thus, the virus excreted in the feces, urine and other secretions of wild hogs could have infected the child.
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