Conjunctivitis in rabbits caused by enterovirus type 70 (EV70).

A rabbit enterovirus 70 (EV70) model infection that closely mimics human enteroviral conjunctivitis was developed. Conjunctivitis occurred 24 hr following topical application of EV70. The conjunctivitis was characterized by tearing, redness, swelling of the eye lids, follicles in the superior palpebral conjunctiva, and dilatation of subconjunctival blood vessels. Histologic examination of conjunctival and corneal tissue taken 1 and 2 days after infection revealed numerous punctate areas devoid of squamous epithelium on the upper palpebral conjunctiva. Also, follicles without germinal centers were observed microscopically in the palpebral and tarsal conjunctiva. Fibroblast infiltration characteristic of wound healing and a sparse mononuclear infiltration was noted by the second day. Peak levels of virus [10(3) to 10(6.2) plaque forming units (PFU)/ml] were detected 1 to 2 days after infection and declined to undetectable levels after 3 to 5 days. Interestingly, antiserum to parental EV70 was less effective (8-10-fold) in neutralizing EV70 adapted to animal and tissue culture systems. This finding suggests that an antigenic variant of EV70 arose during adaptation. Fibroblast interferon (IFN beta), which is indicative of viral infection, was detected in tears from 6 of 16 rabbits and declined to undetectable levels 3 days after infection. Serum antibody to EV70 was detectable 8 to 10 days after infection. However, the level of serum antibody was highly variable. The results indicate that the clinical disease, virologic and immunologic courses were similar to that of the human infection. Results suggest that this animal model provides a system for studying the natural antigenic variation of EV70, the natural host defenses of the eye, and antiviral treatments against enteroviral conjunctivitis.

A recent epidemic of acute hemorrhagic conjunctivitis.

The coxsackievirus A24 variant was implicated in four of six major acute hemorrhagic conjunctivitis outbreaks in Singapore since its discovery in 1970. Hela cell suspension in 24-well flat-bottom tissue culture plates was a satisfactory alternative to monolayer cells grown in test tubes for virus isolation. Respiratory illness occurred in 20 of 98 patients with acute hemorrhagic conjunctivitis. Apart from conjunctival secretions, respiratory and oral transmission of coxsackievirus A24 variant would explain the rapid and extensive spread of acute hemorrhagic conjunctivitis during an outbreak.

A recent epidemic of Coxsackie virus type A24 acute haemorrhagic conjunctivitis in Singapore.

A recent epidemic of acute conjunctivitis in Singapore showed again the importance of Coxsackie virus type A24 variant as a causative agent of acute haemorrhagic conjunctivitis (AHC). Although the ocular manifestations appeared similar to those described for the 1970 and 1975 outbreaks, a markedly higher rate of respiratory involvements was noted. Not observed in previous epidemics were herpes-like vesicles in the conjunctiva and eyelids of one patient and vesicles in the buccal mucosa and lips of another from whom Coxsackie virus A24 was isolated. The most interesting finding in this study was the isolation of five wild (non-Sabin) poliovirus type 1 strains. Three strains were obtained from conjunctival and two from throat swabs of patients with mild to severe conjunctivitis. It is conceivable that the rare reports of polio-like paralysis or radiculomyelitis accompanying or following AHC in a few Asian countries could be attributed to concurrent infections with a poliovirus and either enterovirus type 70 or Coxsackie virus type A24.

Virus-specific, early appearing neutralizing activity and interferon in tears of patients with acute hemorrhagic conjunctivitis.

Virus-specific, early appearing neutralizing activities (ENA) and interferon (IFN) were detected in tears collected from patients during epidemics of acute hemorrhagic conjunctivitis (AHC). In one study, ENA that neutralized enterovirus type 70 (EV70) was detected in tears collected from 114 of 130 AHC patients in Florida. In another study, ENA against coxsackievirus type A24 (CA24) was detected in tears collected from 39 of 57 patients in Singapore with AHC caused by CA24. No tear samples contained ENAs to both EV70 and CA24. Tear samples from uninfected eyes did not contain ENA to EV70 or CA24. ENA to EV70 was detected in 6 of 11 patients 1-6h before the onset of AHC. In addition, tears of 68% of patients seen on the day of onset produced tears that contained ENA to EV70. Thus, ENA to EV70 may be detected less than 24h after infection (based on 24h incubation period). IFN beta was detected in 30% of tear samples collected from patients on the day of onset of AHC caused by EV70. This finding suggested that ENA and IFN could act together to inhibit primary infections of AHC. It was found that the combination of ENA and IFN inhibited virus replication synergistically (greater than or equal to 300 fold reduction) in preinfected cells. Our findings suggest that ENA represents a previously unreported early defense mechanism of the eye, that endogenous ENA and endogenous IFN could inhibit viruses synergistically in vivo, and that ENA in tears could be useful in identifying the agent causing AHC.

Preliminary report on an unidentified virus from infantile myocarditis.

A preliminary report on an unidentified virus from two cases of infantile myocarditis is presented. The virus isolated from two separate occasions showed characteristics of an enterovirus. The significance of this virus in its association with infantile myocarditis requires further investigation.

An outbreak of acute conjunctivitis caused by coxsackievirus A24 in Kuala-Lumpur, Malaysia, 1978.

An investigation of an outbreak of acute conjunctivitis in Kuala Lumpur from May to August 1978 was made. A total of 2,133 cases was involved, most of whom were adult Malay males of low income status from the surrounding villages and low-cost flats. The majority of cases had bilateral conjunctivitis with clear discharge. Pain and subconjunctival haemorrhage were not common and recovery, mostly without complications, occurred within 1 week. Eye scrapings and paired sera specimens were examined and the causal agent was found to be Coxsackievirus A24 (CA24).

An epidemic of acute conjunctivitis caused by enterovirus-70 in Singapore in 1980.

The clinical, epidemiological and virological findings of the 1980 epidemic of acute conjunctivitis were described. Enterovirus 70 was isolated from 7 (35%) of 20 eye swabs submitted for virus isolation, and the paired sera of eight patients showed a four-fold or greater rise in neutralising antibody titre to Enterovirus 70. The disease mainly affected children and young adults of all ethnic groups. Most of the cases contracted the infection at home. The mean secondary attack rate was 72.6% and the mean incubation period, four days. The clinical features were similar to the 1970 and 1975 epidemics caused by Coxsackievirus A24. Subconjunctival haemorrhage was observed in 10% of the cases. Most of the cases recovered spontaneously within a week. Transmission of infection within the home was either indirect, probably through fomites contaminated with eye or respiratory discharges of cases, or direct, through intimate person-to-person contact. During outbreaks, health education on simple personal hygiene should be highlighted.

A coxsackievirus type A24 epidemic conjunctivitis in Brunei.

The paper reports on a coxsackievirus type A24 epidemic of acute conjunctivitis in Brunei. The role of the Singapore Epidemic Conjunctivitis 1970 (coxsackievirus type A24) virus in the new disease syndrome variously known as the "Epidemic Haemorrhagic Conjunctivitis", "Picornavirus Epidemic Conjunctivitis" and "Acute Haemorrhagic Conjunctivitis" is again established.

A coxsackievirus type A24 epidemic of acute conjunctivitis.

The 1975 epidemic of acute conjunctivitis was caused by the return of S.E.C. 1970 virus (CA24). The clinical manifestations of cases seen in the recent epidemic were similar to those seen during the 1970 epidemic caused by S.E.C. 1970 virus (CA24) and the 1971 epidemic caused by S.E.C. 1971 virus (entero-virus type 70). In our opinion, both the S.E.C. 1970 VIRUS (CA24) and S.E.C. 1971 virus (enterovirus type 70) are equally important causes of epidemics of acute conjunctivitis more commonly known as the "Acute Haemorrhagic Conjunctivitis". Although these two enteroviruses affect mainly the eye, apart from conjunctival secretions, they could be transmitted in respiratory droplets and faeces. The authors would prefer to retain the term "Picornavirus Epidemic Conjunctivitis" to denote infection by S.E.C. 1970 virus (CA24) and S.E.C. 1971 virus (enterovirus type 70).

Enterovirus and enterovirus infections.

An account of the nature of enterovirus and enterovirus infections with special reference to experiences encountered in Singapore is presented. The most common of enterovirus epidemic diseases since 1970 is Acute Haemorrhagic Conjunctivitis caused by Coxsackievirus A24 variant and Enterovirus type 70. Enterovirus of various serotypes were isolated from a wide range of illnesses varying in severity throughout the year.

Aetiology of diarrhoea in Singapore.

Stools from acute diarrhoea were investigated for bacterial and viral pathogens. In one study involving 63 young children in a paediatric ward, 70% of the stools were positive for the pathogens looked for of which 37% contained bacteria, 22% viruses and 11% mixed cultures of bacteria and viruses. In another study in which 130 watery stools from routine specimens of patients of all ages were investigated, 36% were positive for pathogens with 11% bacteria, 18% viruses and 7% mixed pathogens. The high incidence of bacterial diarrhoea in young children was attributed to gastroenteritis caused by Salmonella species. Salmonella and rotavirus were found the most common pathogens in bacterial and viral diarrhoeas, and the most susceptible age group was under 5 years-old.

Poliovirus neutralising antibody in infants and cord blood.

Singapore participated in the WHO EPI protocol for rapid assessment of serological response to three doses of standard oral poliovirus vaccine. The 100% seropositive finding of thirty infants below one year old is no proof of seroconversion rate to the Trivalent Oral Poliovirus Vaccine (TOPV) administered. Investigation of 100 cord blood samples showed that passively transferred maternal poliovirus neutralising antibody cannot be relied upon for protection of infants against poliomyelitis. This paper emphasises the importance of vaccine potency testing and serves as a timely reminder that although the last case of indigenous poliomyelitis was recorded in 1974, non Sabin-like (wild) polioviruses are being isolated from imported cases and foreigners hospitalised in Singapore, and unexpectedly, from the conjunctiva and pharynx of Singaporeans treated for conjunctivitis. It discusses the WHO (World Health Organization) Plan of Action for Eradication of Polio in the Western Pacific Region which includes Singapore.