PRESUMPTIVE RAPID DIAGNOSIS OF PARVOVIRUS INFECTION IN PATIENTS WITH ERYTHEMA INFECTIOSUM-LIKE ILLNESS

: In September 1987 an outbreak of exanthematous illness ressembling erythma infectiosum occurred at an elementary schoo1 ofSão Paulo city. Attempts to iso1ate virus from the nasofaryngeal secretion and urine and serum samples collected from the ill chi1dren in acute phase ofillness resulted negative. Nevertheless, parvovirus-like partic1es of about 24 nm in diameter were observed by negative staining electron microscopy in concentraded urine of seven out of eight i1lpatients and in nasopharyngeal secretion of one out of four patients. No similar viral partic1e was observed in concentred urine samples collected on the same occasion from their c1assmates without evident signs ofillness. This is a proposal of an altemative test for a rapid and sensitive presumptive diagnosis ofhuman parvovirus infection.


INTRODUCTION
It is generaly accepted that human 8arvovirus B 19, discovered by Cosart et ai. in 1975 1 ,is the cause of erytema infectiosum 4, 16, 19.It ais o became apparent that the infection by this virus may be associated with arthralgia, aplastic crisis 3 ~ontaneous abortion and intra-uteríne fetal death:" ,6,7,20,22.Asymptomatic infection has been reported in household members lO , 19.Antibody to human parvovirus is most often acquired within the age of5 and 10 yers and about 60% of blood donor poplation are seropositive 2 ,7.Parvovirus B 19 seems to be widespread throughout the world.Seroprevalence studies indicated that 25-40% of adults in Europe and in the United States, as well as in Australia j Africa and Brazil had antibodies to this virus " 1 , 15 .Fifth disease outbreak have been reported from England.Japan, Finland and Canada and most of the cases occurred in late winter and early spring 4 ,12,15,19 .ln Brazil, the evidence of B 19 virus infection in cases of erythema infectiosum was firstly obtained in Belem by the IgM antibody assay 13.
The inability to grow parvovirus B 19 in sufficient quantity to produce antigen for diagnostic .irus an igen has been detected by counterimmunoelectrophore-.di .
10 SIS, ra roimmunossay or enzyme immunoassay .Viral DNA has been detected by dot-blot hybridisation and more recently by the use of polymerase chain reaction assay (PCR)8, 14,23.The presence of parvovirus particles may be detected in sera and respiratory secretion by electron microscopy and viral DNA was also found in the urine of this patients.3 ,7 In September 1987, an outbreak of exanthematous febril illness clinically and epidemiologically suggestive of erythema infectiosum occurred at an elementary school of Municipal Area of São Paulo City in the Sanitary District of Butantã.About 50 children ofboth sex attending the school within the age of 7 to 9 years were affected by the illness.The clinical symptoms were maculo-papular exanthem in the face and lacy reticular aspect in the torax and superior members.The fever was low around 37.SoC or absent in some children.Among the chidren , four had only slapped cheek and four had erythema in both face and limbs.
With aim to investigate the etiologic agent if ill patients were inoculated into tubes of Hep2, BHK-21 MCR-5 Vero and MDCK cell cultures.The virus is~lation at{emps in these cell cultures resulted negative.
Based on previous studies that the human parvovirus B 19 is the etiologic agent of erythema infectiosum, the clinical specimens were tested for the presence of parvovirus particles.Urine of eight children and nasopharyngeal secretion (NPS) and sera of four children of a total of 12 students with erythema infectiosum, and urine of 15 asymptomatic children were examinted for the presence of parvovirus-like particle by negative staining electron microscopy.The urine samples were previously concentrated 100 to 400 times by Minicon B15 (Amicon Co).Viral particle measuring about 24 mm were detected in the urine of seven il patients.Four urine samples were positive after concentrating 100X, but three specimens needed 400X concentration before the viral particles being detected, and one was negative.Viral particles of similar size and morphology were seen in the NPS of one out of four children studied, but none was found in the sera ofthese children.Otherwise the attempts to find similar viral particles in sera and urines 15 asymptomatic classmates collected on the same occasion resulted negative.

DISCUSSION
Other viruses are also associated with exanthems as enteroviruses, Herpesvirus Group, adenoviruses, measles virus, rubella virus, although differing of B 19 infection in both clinical and epidemiological aspects.The possibility of the illness in the present investigation being caused by rubella virus, measles virus or Herpesvirus Group was discarted because they have envelope in the outer membranes and are larger than the virus found in the present investigation (rubella measures virus, 58 mm, measles virus, 150-400 mm and Herpesvirus Group 160-200 mm).Enteroviruses and adenoiruses are cultivable in the virus isolation system utilized in this study.
It seems that erythema infectiosum is a relatively late event in parvovirus B 19 infection.This may explain the fact that no viral Bl9-like particle was found in sera of these patients and this is in accord-.h .di 49 ance wit previous stu ies " .
Examination of urine for the presence of microorganism helps in the diagnosis of certain infectious diseases.The success of detection viruses depends upon the amount ofvirus being excreted in the urine.It is possible that if the virus is excreted in urine in low number, the commonly used procedures may not be sensitive enough to detect it.However, ifthe urine sample is concentrated prior to being tested, the probability of virus detection may increase considerably'".Minicon B-15 (Amicon Co.) has been used for concentration of urine, cerebrospinal fluid or other physiological fluid 18.It contains membranes with a cut-off of 15,000 molecular weight, being able to retain the smallest viral particles and even proteins.RESUMO: Em setembro de 1987 ocorreu em uma escola primária municipal da cidade de São Paulo, um surto de doença exantemática clinicamente compatível com eritema infeccioso.As tentativas de isolamento de vírus de amostras da nasofaringe, urina e soro de doentes colhidos na fase aguda da doença resultaram negativas.No entanto, partículas virais de cerca de 24 nm de diâmetro semelhantes ao parvovírus foram observadas ao microscópio eletrônico pela coloração negativa em sete das oito amostras e na secreção da nasofaringe de uma das quatro amostras colhidas de doentes.Por outro lado não foi visualizada nenhuma partícula viral semelhante em amostras de urina igualmente concentradas, colhidas na mesma ocasião de 15 colegas de classe que não apresentavam sinais evidentes da doença.A presente investigação apresenta uma alternativa para diagnóstico presuntivo rápido de infecção por parvovírus humano.DESCRITORES: Eritema infeccioso.Infecção por parvovírus.Diagnóstico presuntivo.