Human parvovirus B19 infection among children wi

　　 作者：Girei AI1， Alao OO2， Joseph DE3， Damulak DO3， Banwat EB4， Nwadioha SI5， Jombo GTA5　　

【摘要】 Objective:Human Parvovirus B19 is known to cause significant morbidity and mortality and among perse patient population groups. Among patients with sickle all disease， who have high red cell turn over due to chronic haemolysis， infection with parvovirus B19 can cause severe life threatening transient aplastic crisis. This study was conducted to determine the Seroprevalence of parvovirus B19 infection and to provide basic epidemiological data on parvovirus B19 infection among children with sickle cell anaemia in Jos， north central Nigeria. Methods: In a hospital based cross sectional survey， 200 children aged 118 years confirmed to have sickle cell anaemia attending the paediatric sickle cell clinic of Jos university teaching hospital were studied. A questionnaire was designed to obtain basic sociodemographic information， && other relevant aspect of patients′ history. Blood samples were taken for anti parvovirus B19 serology. Results: The over all prevalence rates of parvovirus B19 immunoglobulin (IgG) and immunoglobulin (IgM) antibodies were 39.5% and 3.5% respectively， Conclusion: This study confirms that parvovirus B19 infection is prevalent among children with sickle cell anaemia in Jos， North Central Nigeria. There is a need for further studies to fully evaluate the clinical impact of the infection on our sickle cell anaemia patients.

【关键词】 Human; Parvovirus B19; Sickle cell anaemia; Jos

　Introduction

　　Human parvovirus B19 is the only member of parvoviridae family known to be pathogenic to man[1]. Since its accidental discovery about 30 years ago， parvovirus B19 has increasingly been recognized as an important human pathogen causing significant morbidity and mortality among various population groups[2].

　　Manifestations of parvovirus B19 infection vary with the immunologic and haematologic status of the host. In otherwise healthy immunocompetent schoolage children， it is the cause of erythema infectiosum， also known as fifth disease， an innocuous exanthematous rash that affects the face， trunks and limbs of the body. In otherwise health adults， infection is occasionally associated with an acute symmetric poly arthropathy resembling Rheumatoid arthritis .

　　In patients with chronic haemolytic states like sickle cell disease， in whom there is high turn over of erythrocytes， acute infection frequently causes transient red cell aplasia also known as aplastic crisis， leading to severe anaemia. Although such crisis is self limiting in most patients， life threatening anaemia may occasionally occur， necessitating urgent blood transfusion. Further more， case studies have strongly linked acute parvovirus B19 infection to other life threatening and often potentially fatal complications of sickle cell disease， like acute chest syndrome[3]， splenic sequestration[4]， and meningoencephalitis[5]. In the immunocompromised host as in patients with the Acquired immunodeficiency syndrome (AIDS)， persistent parvovirus B19 infection is manifested as pure red cell aplasia leading to chronic transfusion dependent anaemia.

　　It is worthy of note that sickle cell anaemia is a major public health concern in Nigeria with an estimated prevalence rate at birth of 2%. It is further observed that accurate data on the frequency of parvovirus B19 infection among patients with sickle cell anaemia is lacking in most parts of Nigeria. To the best authors′ knowledge there is no published work on even the most basic epidemiologic profile of parvovirus B19 infection in this part of Nigeria. This study therefore was designed to determine the Seroprevalence rate of human parvovirus B19 in children with sickle cell anaemia in Jos， north central Nigeria

　　Materials and Methods

　　Two hundred consecutive children aged 1 to 18 years who attended the paediatric sickle cell clinic in JUTH between January and November 2009， who met the inclusion criteria were recruited into the study. Their blood samples were screened for presence of parvovirus IgG and IgM antibodies. All tests were done using ELISAbased kits manufactured by "institute virion/serion GmbH Wurzburg， Germany".

　　Ethicsnormal protocol for the approval of the study by the research and ethical committee of JUTH， Jos was followed. The study is invasive， so informed consent was obtained from all participants. The data were analyzed using Epi info computer software version 2.2.1 Simple proportion was used to determine prevalence.

　　Results

　　A total of 200 children aged 1 to 18 years with a diagnosis of sickle cell anaemia who presented to the sickle cell clinic in the period were screened. The socio demographic characteristics of subjects are summarized in table 1. One hundred and eight (54.0%) were males while 92 (46.0%) were females giving a male: female ratio of 1.17∶1. Most of the children， 93% (186/200)， were under 15 years. The mean age of the study population was 6.8(±4.6) years. Out of the 200 samples subjected to parvovirus serology， 79 were positive for anti parvovirus B19 Ig G antibody， giving an overall Seroprevalence rate of 79/200 or 39.5%. The agespecific Seroprevalence rates are shown in table 2. The prevalence rate was lowest (21.7%) in the age group 15 years. It increased with age， reaching over 90% in the 1620 year old age group. Of the 200 samples screened for anti parvovirus B19 IgM antibodies， seven (3.5%) were positive. Their agegender distribution is shown in table 3. They consisted of five males and two females; three patients were in the age group 610 years， while two were in the 1620 year age group. There was one patient each in the age groups 15 and 1115 respectively. All seven patients who tested positive for anti IgM parvovirus B19 antibody were also positive for parvovirus B19 IgG antibody.Table 1 Age and sex distribution of Table 2 Anti parvovirus B19 Ig G Seroprevalence among children with sickle cell anaemia in JosTable 3 Anti parvovirus B19 IgM Seroprevalence among children with sickle cell anaemia in Jos

　　Discussion

　　Human parvovirus B19 is a common human pathogen occurring in all regions of the world. Most of published information on the epidemiology of the virus is based on studies done in the healthy general population. This study is one of the few that focused on children with sickle cell disease (SCD) –a special patient population group known to be profoundly affected by the consequences of infection with parvovirus B19[1].

　　The over all prevalence rate of anti parvovirus B19 IgG antibody established in this study was 39.5%. It ranged from 21.7% in the 15 year agegroup， gradually increasing with age to 92.8% in the 1620 yeas old agegroup. Although the very high prevalence rate in the 1620years old group could be attributed to the lower number of patients in that group， it is evidently clear that over 60% of children are seropositive by the time they reach 15years. This suggests that parvovirus B19 is endemic in our environment. To the best of authors′ knowledge， there is no published national data on the prevalence of parvovirus B19 that may be used to compare the results of this study with. However， the result from this study compare well with the finding in Jamaica， a tropical country in the Caribbean， where an over all IgG point prevalence rate of 37% was found at the start of a cohort study among children with sickle cell anaemia.

　　Girei AI et al. Human parvovirus B19 infection among children with sickle cell anaemia in Jos， North Central Nigeria

　　The Seroprevalence rate obtained in this study also falls within the range (35%70%) reported from different serosurveys among the general healthy population in different regions of the world[6]. However， a rather lower Seroprevalence rate (29.8%) was reported from a study also on children with SCD in Philadelphia， a temperate region of the world in northeastern united states of America[7]. This may reflect true epidemiologic differences between children with sickle anaemia in tropical and temperature regions of the world. In both studies， it is interesting to note that seropositivity rates also increased gradually with increasing age. This study has established anti parvovirus B19 IgM Seroprevalence rate of 3.5% among children with sickle cell anaemia in Jos. Compared to IgG seropositivity rates， IgM seropositivity is fairly distributed among all age groups. This is somewhat surprising as it is expected that the younger age groups would bear most of the burden of acute infection (reflected by IgM seropositivity rate) because of their lower immunity to parvovirus B19. The IgM Seroprevalence rate obtained is this study compares with results of similar cross sectional studies in other parts of the world. For example， Thai workers reported an IgM Seroprevalence rate of 40% among thalassaemic patients in steady state[8]. A population based serosurvey among healthy children in Papua New Guinea[9] however found a lower Seroprevalence rate (1.5%)， while studies of adult blood donors in the USA， also reported a low prevalence rate (1%).

　　The IgM Seroprevalence rate obtained from this study appears low when considered against the backdrop of a high 1gG Seroprevalence in the same population. However， when one considers the fact that in many regions of the world parvovirus B19 transmission follows a seasonal pattern with outbreaks every three to six years[10]， it may be possible that the timing of this study corresponded to a period of low transmission in our environment. It is important to emphasize also that although parvovirus B19 IgM antibody positivity is indicative of an acute infection in an inpidual， the prevalence rate obtained in the study (which is cross sectional in design) may not be a true reflection of the magnitude of acute parvovirus B19 infection in children with sickle cell anaemia in our environment.

　　In conclusion， this study has established that infection with parvovirus B19 is prevalence among children with sickle cell anaemia is Jos， Northcentral Nigeria. Clinicians caring for patients with SCA should be more aware of the existence of parvovirus B19 in our environment. To decisively evaluate the clinical effects of this virus among patients with SCA， prospective cohort studies among these patients are recommended. Since many other patient groups are also vulnerable， large scale community based survey should be undertaken to determine the true magnitude of parvovirus B19 infection in our communities.

参考文献

　　1 Amy CP. Parvoviruses erythema infectiosum， aplastic crisis. In: Mandell GL， Bennett JE， Dolan R， editors. Mandell douglas， and bennetts principle and practice of infectious diseases. 4th ed. New York: Churchill Livingstone， Vol ii 2000.14931443.

　　2 Anderson LJ. Role of parvovirus B19 in human disease. Pediatric Infectious Disease Journal，1987，6:711781.

　　3Lowenthal EA， Wells A， Emmanuel PD， Player R， Prchal JT.Sickle cell acute chest syndrome associated with parvovirus B19 case series and review. American Journal of Hematology，1996，51:207213.

　　4 Mallouh AA， Quadah A. Acute splenic sequestration together with aplastic crisis caused by human parvovirus B19 in patients with sickle cell disease. Journal of Pediatrics，1993，122:593595.

　　5 Wierenga KJ， Serjeant BE， Serjeant BR. Cerebrovascular complications and parvovirus infection in homozygous sickle cell disease. Journal of Pediatrics，2001，139:438442.

　　6 Kelly HA， Siebert D， Hammond R， Leydon J， Kiely P， Maskill W. The agespecific prevalence of human parvovirus immunity in victoria Australia compared with other parts of the world. Epidemiology and Infection，2000，124:449457.

　　7 SmithWhitley K， Zhao H， Hodinka LR， Kwiatkoski J， Cecil T， Cnaan A， et al. Epidemiology of human parvovirus B19 in children with sickle cell disease. Blood，2004， 103:422427.

　　8 Sirintantikorm S， Kaewrawang S， Sirintanaratkul N， Theamboonlers A， Poovorawan Y， Kantakamalakul W ，et al. The prevalence and persistence of human parvovirus B19 infection in thalassaemic patients. Asian Pacific Journal of Allergy and Immunology，2007，25:169174.

　　9 Wildig J， Mueller I， Kiniboro， B， Maraga S， Siba P， Cossart Y. Seroprevalence of antibody to parvovirus B19 among children in Papua New Ginea. American Journal of Tropical Medicine and Hygiene，2007，77(2):354357.

　　10 Nicolay N， Cotter S. Clinical and epidemiological aspects of parvovirus B19 infections in Ireland， January 1996June 2008. Eurosurveillance 2009: 14 (25): pii=19249. Available online:http//www.eurosurvelliance.org/ViewArticle.aspx?Articleld=19249 (updated 2009 June 25， accessed 2009 Nov.5).