Excluding polio in areas of inadequate surveillance in the final stages of eradication in China

In 1996, China adopted a virological classification of acute flaccid paralysis (AFP) cases for its surveillance system. Only AFP cases with wild poliovirus in stool specimens are confirmed as polio. Cases with adequate stool specimens that are negative for wild poliovirus are not counted. This paper describes a methodology to rule out poliomyelitis in AFP cases with inadequate stool specimens. National surveillance data were analysed using dot maps to detect clusters of AFP cases with high-risk factors for poliomyelitis. The surveillance system and vaccine coverage were assessed during field investigations. Four clusters of AFP cases were identified, but no poliomyelitis cases. Programmatic failures in the identified high-risk areas included low vaccination rates, poor stool specimen collection and inadequate AFP surveillance. Programme strategies were implemented to correct the identified failures. Use of this methodology provides strong evidence consistent with the absence of wild poliovirus in China.

Surveillance of patients with acute flaccid paralysis in Finland: report of a pilot study

WHO recommends that surveillance of patients with acute flaccid paralysis (AFP) be used to demonstrate the eradication of wild poliovirus. In this article we report the results of a study to assess the frequency of AFP patients referred to Finnish hospitals and whether virological diagnostic coverage could be improved by repeated reminders and active feedback. For this purpose, we sent monthly questionnaires to all neurological and paediatric neurological units in Finland, requesting retrospective reporting on investigated paralytic patients with defined clinically relevant diagnoses, rather than AFP. Reminder letters included a pre-paid return envelope. Virological investigations were offered cost free. Of the 492 reporting forms sent, 415 (84%) were returned, evenly covering both the population and the study period (July 1997 to June 1998). Of the 90 patients reported, 83 were evaluable. The apparent incidences of the diagnoses covered were 1.6 per 100,000 at any age, and 1.0 per 100,000 for under--15-year-olds. Guillain-Barré syndrome was the most common diagnosis (0.80 per 100,000). The two faecal specimens required were virologically investigated in nine out of the 10 patients under 15 years of age, but in only 46% of all patients. Four adenovirus strains, but no polioviruses or other enteroviruses, were isolated. We conclude that a satisfactory monthly reporting system was readily established and that a sufficient number of patients with diagnoses resembling AFP are being referred to Finnish hospitals. Active feedback did not increase the proportion of virologically investigated patients to an acceptable level in all age groups. It is clear that other approaches must be used to quantify the circulation of poliovirus in Finland.

Poliomyelitis surveillance: the model used in India for polio eradication

Poliomyelitis surveillance in India previously involved the passive reporting of clinically suspected cases. The capacity for detecting the disease was limited because there was no surveillance of acute flaccid paralysis (AFP). In October 1997, 59 specially trained Surveillance Medical Officers were deployed throughout the country to establish active AFP surveillance; 11,533 units were created to report weekly on the occurrence of AFP cases at the district, state and national levels; timely case investigation and the collection of stool specimens from AFP cases was undertaken; linkages were made to support the polio laboratory network; and extensive training of government counterparts of the Surveillance Medical Officers was conducted. Data reported at the national level are analysed and distributed weekly. Annualized rates of non-polio AFP increased from 0.22 per 100,000 children aged under 15 years in 1997 to 1.39 per 100,000 in 1999. The proportion of cases with two adequate stools collected within two weeks of the onset of paralysis increased from 34% in 1997 to 68% in 1999. The number of polio cases associated with the isolation of wild poliovirus decreased from 211 in the first quarter of 1998 to 77 in the first quarter of 1999. Widespread transmission of wild poliovirus types 1 and 3 persists throughout the country; type 2 occurs only in Bihar and Uttar Pradesh. In order to achieve polio eradication in India during 2000, extra national immunization days and house-to-house mopping-up rounds should be organized.

Report of the Australian National Polio Reference Laboratory. 1 January 1999 to 30 June 1999. Towards WHO certification as wild poliovirus-free: laboratory surveillance in Australia

Since 1994 the Australian National Polio Reference Laboratory at the Victorian Infectious Diseases Reference Laboratory has been responsible for virological confirmation of the eradication of poliomyelitis in Australia. The laboratory is also a World Health Organization Western Pacific regional polio reference laboratory and the national polio laboratory for the Pacific Island countries and for Brunei Darussalam. It is now over two years since the last case of poliomyelitis was detected in the Western Pacific region of the World Health Organization. The co-operation of staff in all laboratories where polioviruses are handled and where samples from acute flaccid paralysis (AFP) patients are submitted is required until Australia and the region can be declared wild poliovirus-free. The characterisation of all polioviruses isolated in Australia in this reporting period led to the apparent detection of a non Sabin vaccine-like poliovirus in an environmental sample. The virus was found to be identical to a laboratory control isolate by sequencing. The environmental virus is therefore characterised as a contaminant, not a wild isolate. The investigation is outlined in this article, as well as the results of investigation and characterisation of all referred polioviruses.

Four distinct neurologic syndromes in Marek's disease: effect of viral strain and pathotype

A chronological study of central nervous system disorders induced by Marek's disease virus (MDV) has been conducted. Neurologic clinical signs were recorded daily for individual chickens of two genetic lines after inoculation of 13 serotype 1 MDV strains representing all three pathotypes. In addition to classical transient paralysis (TP) previously described by many workers, and acute TP, described in the companion paper, we have identified for the first time two other neurologic syndromes, persistent neurologic disease (PND) and late paralysis (LP). PND designates birds that showed a variety of neurologic signs (ataxia, torticollis, and nervous tics) after recovery from paralysis (12-15 days postin-oculation [DPI]) that either persisted through the observation period or presented a cyclic pattern. LP was a rare syndrome characterized by the late onset of the paralytic stage (about 20 DPI), perhaps indicating occasional failure of the initial intraabdominal inoculation to induce infection. Clinical signs and histopathologic alterations of the brain were also evaluated sequentially in chickens of two genetic lines after inoculation with two MDV strains (virulent MDV and very virulent plus MDV). Although clinical response differed greatly among treatment groups, types of lesions (endotheliosis, mononuclear perivascular cuffing, vasculitis, vacuolization, and increase in cellularity of the neuropil) were similar. However, early onset of lesions (by 6 days) appeared to be associated with a greater severity of clinical signs. We also found that neurologic response was greatly influenced by viral pathotype (virulence). This study thus confirms that the central nervous system is an important target organ for MDV resulting in several distinct clinical manifestations and suggests that neurologic responses in antibody-free chickens might be a useful criterion for virus pathotyping.

An acute form of transient paralysis induced by highly virulent strains of Marek's disease virus

A novel syndrome was observed after inoculation of 3-wk-old chickens with highly virulent Marek's disease virus (MDV) strains. This syndrome was characterized by the acute onset of neurologic signs including flaccid paralysis of neck and limbs 9-10 days postinoculation, typically resulting in death 1-3 days after the onset of clinical signs. Most affected birds died, and spontaneous recovery was rare. Few if any gross tissue changes were found. Histologic brain lesions included acute vasculitis with vasogenic edema and perivascular cuffing. The syndrome was influenced by the virus strain and dose and by chicken strain and B haplotype and was prevented by vaccination with turkey herpesvirus. Chickens up to 18 wk of age were susceptible. On the basis of clinical signs and histopathology, the syndrome was determined to be an acute form of transient paralysis (TP); its more acute nature and virtual lack of spontaneous recovery differentiated this syndrome from classical TP. Affected birds were viremic, and brains were positive for viral DNA by polymerase chain reaction assays, but these tests were also positive in inoculated chickens without clinical signs and may have limited value for diagnosis. Although acute TP should occur only rarely in Marek's disease-vaccinated commercial flocks, this syndrome may be important in laboratory studies, where it could interfere with pathogenesis trials. Finally, acute TP appears to be one component in the pathogenesis of the early mortality syndrome, a previously described immunodepressive disease induced by inoculation of 1-day-old chicks with highly virulent MDV.

Molecular epidemiology of poliovirus infection in Tunisia

This report is an overview of poliomyelitis surveillance in Tunisia from 1991 to 1996. In all, 2088 stool specimens, collected from 152 acute flaccid paralysis (AFP) cases and from 1747 of their healthy contacts were investigated. Virus isolation was done systematically in RD and HEp-2C cell lines and isolated viruses were typed by sero-neutralisation as polioviruses or non-polio enteroviruses. Poliovirus isolates were analysed systematically for their wild or vaccine-related origin by two methods--one based on antigenic differences and one on genetic differences between strains. All type 2 polioviruses were vaccine-related and most wild viruses belonged to polio serotype 3. Wild polio type 3 viruses were detected in 1991 and 1992 in six cases of paralytic polio. A silent circulation of wild polio 1 and wild polio 3 was detected in 1994. No wild virus was detected in Tunisia from 1995 onwards. Wild polioviruses were sequenced and compared with Tunisian wild strains isolated during the 1980s, as well as other genotypes from the international database. These investigations revealed a single Tunisian polio 3 genotype that has been circulating from 1985 to 1994 and two different polio 1 genotypes. These results reflect effective control strategies within the country and contribute to the improvement of the polio eradication programme effectiveness at national and global levels.

Selective antibody neutralization prevents neuropathogenic lactate dehydrogenase-elevating virus from causing paralytic disease in immunocompetent mice

Neuropathogenic lactate dehydrogenase-elevating viruses (LDV) cytocidally infect anterior horn neurons in C58 and AKR mice via interaction with endogenous murine retroviruses to cause a paralytic disease, age-dependent poliomyelitis (ADPM). The induction of ADPM requires a suppressed host immune system as a result of old age, genetic defects (such as nude mice) or any immunosuppressive treatment. Previous results have shown that the infection of anterior horn neurons by neuropathogenic LDV isolates and the subsequent development of ADPM are prevented by anti-LDV antibodies either induced actively during infection or when passively administered. However, the mechanism of protection was unclear since both neutralizing and non-neutralizing polyclonal antibodies seemed protective, whereas only neutralizing monoclonal antibodies were protective. Furthermore, the protection of motor neurons from infection occurred in the absence of any apparent effect on LDV replication in a subpopulation of macrophages known to be the primary permissive host cells. These paradoxes have now been resolved. We have recently reported that the neuropathogenic LDV isolates contain both neuropathogenic and non-neuropathogenic quasispecies that differ in their ability to establish a high viremia persistent infection. Using biological clones of both neuropathogenic and non-neuropathogenic quasispecies, we now demonstrate that both replicate in the same subpopulation of permissive macrophages, but that the neuropathogenic quasispecies are about 100 times more susceptible to in vitro antibody neutralization than the non-neuropathogenic ones, and that antibodies that neutralize the neuropathogenic but not the non-neuropathogenic quasispecies develop as soon as 7 days after infection with neuropathogenic LDVs and selectively suppress the replication of the neuropathogenic LDVs in vivo in FVB, BALB/c, C57 BL/6 and C58 mice. The previously observed lack of neutralizing effect of early polyclonal anti-LDV antibodies and the apparent ineffective antibody control of LDV replication in macrophages were due to outgrowth of the non-neuropathogenic quasispecies that are also present in the neuropathogenic LDV inoculum and are highly resistant to antibody neutralization. Using cloned neuropathogenic LDV quasispecies, we demonstrate a clear relationship in the development of neutralizing antibodies, replication suppression of the neuropathogenic LDVs and the prevention of ADPM in C58 mice. Our results therefore establish an inseparable relationship between the neuron-protective effect of an antibody and its neutralization of the neuropathogenic LDV quasispecies and explain why neuropathogenic LDVs cause paralytic disease only in immunosuppressed mice.

[A case of diagnosis of Landry ascending paralysis of herpetic etiology]

One clinical and pathomorphologic case of Landry paralysis with a proven etiological role of herpetic infection is reported. Acute clinical syndrome developed as a manifestation of exacerbation of chronic inflammation in the central nervous system. Advancement of the process and generalisation of herpetic infection was connected with immunodeficiency in this patient.

[Analysis of clincal poliomyelitis in Shandong Province from 1993-1996]

Wild poliovirus has not been isolated in Shandong province since Apr. 1991. However, 71 clinically polio cases were diagnosed by an expert group, including 50 potential Vaccine Associated Paralytic Poliomyelitis (VAPP) including 31 having the sabin strain in the stools, from 1993 to 1996. The overall frequency of VAPP was one case per 1.25 million doses distributed. The relative frequencies of first dose in the OPV series was one case per 218,800 doses vs one case per 1.01 million for second dose. Based on data from the 31 cases, we estimated that the rates had been one case per 438,000 first dose and one case per 6.42 million second dose and one case per 10.44 million among the contacts of the cases. This results seemed to be higher than from other reports. Clinically confirmed poliomyelitis cases in Shandong were diagnosed by the experts group. The classification of clinical polio cases is important in the polio eradication program.

Antibodies to human myelin proteins and gangliosides in patients with acute neuroparalytic accidents induced by brain-derived rabies vaccine

Antibody responses to myelin antigens were analysed in 15 patients who developed acute neuroparalytic accidents (ANPA) during post-exposure rabies vaccination using a rabies vaccine prepared on brain tissues and in 30 individuals who were uneventfully vaccinated. High titers (> or = 100) of IgG and IgM antibodies to GM1 or GD1a gangliosides were detected by enzyme linked immunosorbent-assay (ELISA) in plasmas from ANPA patients but not in controls. These data suggest that antibodies to GM1 and GD1a gangliosides may play a pathogenic role in the demyelinating and/or inflammatory processes characteristic of rabies vaccine-induced acute neurologic complications.

An epidemic of Newcastle disease in double-crested cormorants from Saskatchewan

A Newcastle disease epidemic in double-crested cormorants (Phalacrocorax auritus) occurred in July and August 1995, during a 1994-96 study of a breeding colony of this species on Doré Lake (Saskatchewan, Canada). Clinical signs and mortality were observed from a tunnel-and-blind system, and moribund and freshly dead birds were examined virologically. Yolks from cormorant eggs and sera from cormorants and other birds were tested for hemagglutination inhibiting antibodies to Newcastle disease virus (NDV). Evidence of Newcastle disease was limited to juvenile double-crested cormorants, despite close contact with other birds, including American white pelicans (Pelecanus erythrorhynchos) and gulls (Larus spp.). Clinical signs included limb, head or neck paralysis, head or body tremors, ataxia, and blindness; pathogenic NDV was isolated from affected birds. The mortality rate of juvenile cormorants was 32 to 64%, which was high relative to overall first-year mortality in years without epidemics. Thirty-seven of 63 (59%) cormorant sera collected during the epidemic tested positive for antibodies to NDV. Antibody status of cormorant egg yolks depended on stage of incubation, likely due to changes in the amount of water in the yolks. The departure of juvenile cormorants from their nests at 4 wk of age, resulting in an increased contact rate among individuals, may have been important in triggering the epidemic.

[Ataxia and paralysis in meat chickens, as a result of an infection with avian encephalomyelitis virus in the breeding flock]

An outbreak of avian encephalomyelitis (AE) in 7 broiler flocks, with signs of ataxia and paralysis is reported. The diagnosis was made by immunofluorescence, histopathology and virus isolation. The breeding flock had a temporary drop in egg production and reduced hatchability caused by late embryonic mortality. The breeding flock had not been vaccinated against AE. The problems were probably caused by vertical transmission of AE virus.

Surveillance of suspected poliomyelitis in Albania, 1980-1995: suggestion of increased risk of vaccine associated poliomyelitis

Surveillance of suspected poliomyelitis cases was conducted in Albania from 1980 through 1995. A total of 93 cases were reported, 11 of which were clinically defined as poliomyelitis cases according to WHO criteria. Poliovirus was isolated from six subjects who were defined as contact vaccine-associated cases. Characterization of isolates by both antigenic and molecular methods showed that, in all cases, the disease was associated with type 2 or 3 polioviruses of vaccine origin with retromutations known to be associated with loss of Sabin attenuated phenotype. Infection occurred despite the fact that all patients had records of previous immunization with oral polio vaccine (OPV), suggesting a failure of vaccination. Four of the five patients from which poliovirus could not be isolated were classified as possible recipient vaccine-associated poliomyelitis on the basis of serology data (presence of antibodies against all three polioviruses) and the temporal association between the latest dose of vaccine received and onset of paralysis. Virological investigation on healthy contacts of the poliomyelitic patients yielded the isolation of a further 12 Sabin-like polio revertant viruses, mostly type 2 and 3. A detailed study of the non-polio acute flaccid paralysis (AFP) cases and their healthy contacts revealed the presence of several enteroviruses, namely Echo, coxsackie and, in three cases type 2 or 3 Sabin-like polioviruses. Overall, these data suggest the absence of circulation of wild-type poliovirus in Albania from 1980 to 1995, before the recent outbreak of poliomyelitis in 1996, and emphasize the need for active surveillance of AFP and laboratory characterization of virus isolates to monitor vaccination efficacy.

The entire nucleotide sequence of friend-related and paralysis-inducing PVC-441 murine leukemia virus (MuLV) and its comparison with those of PVC-211 MuLV and Friend MuLV

PVC-441 murine leukemia virus (MuLV) is a member of the PVC group of Friend MuLV (F-MuLV)-derived neuropathogenic retroviruses. In order to determine the molecular basis for the difference in neuropathogenicity between PVC-441 and the previously characterized PVC-211 MuLVs, the entire nucleotide sequence of PVC-441 MuLV was determined and compared with those of PVC-211 and F-MuLV. The results suggest that PVC-441 and PVC-211 MuLVs were formed as a result of random mutations of F-MuLV and developed differently. The distinct pathogenicities of PVC-441 and PVC-211 MuLVs were maintained in the viruses regenerated from their molecular clones, and the sequences responsible for the pathological differences observed can be localized to the env gene. The amino acid sequence of PVC-441 deduced from its nucleotide sequence revealed a number of differences from PVC-211, the most striking of which was a difference at position 129 of the SU proteins in the two viruses. Host range studies with a brain capillary endothelial cell line (RTEC-6) and Chinese hamster ovary cells (CHO-K1) revealed that PVC-441, like PVC-211, could infect these cells but its efficiency of infection was lower than that of PVC-211. These results may account for the difference in neuropathogenicity between PVC-441 and PVC-211.

Reversible palsy of the hypoglossal nerve complicating infectious mononucleosis in a young child

We report a 7-year-old boy with serologic evidence of active Epstein-Barr virus (EBV) infection who developed transient unilateral hypoglossal nerve palsy, with complete recovery within 21 days. This is, to our knowledge, the youngest reported patient with isolated hypoglossal nerve palsy in the context of EBV infection. Acute EBV infection should be considered early in the evaluation of children with twelfth nerve palsy in order to avoid extensive ancillary testing.

Enterovirus 71 infection and acute neurological disease among children in Brazil (1988-1990)

Surveillance for Enterovirus 71 (EV-71) infection in children up to 15 years of age was carried out in Brazil, from 1988 to 1990. Patients with acute neurological diseases (AND) such as flaccid paralysis, Bell's palsy, acute cerebellar ataxia and Guillain-Barré syndrome were included in the study. EV-71 infection was detected in 24 of 426 children (5.6%) with AND. EV-71 infection was confirmed only by virus isolation in 13 children, by virus isolation and seroconversion in 4, and by seroconversion alone in 7. EV-71 was also isolated from 15 of the 427 household contacts (3.5%) of 165 AND patients. There was some evidence of high infectivity of EV-71: household clusters were detected in the case of 7 of 24 children (29.1%) infected with EV-71 and manifesting AND; EV-71 was isolated from 11/40 household contacts (27.5%) of the infected patients but from only 4/387 household contacts (1.0%) of children in whom it was not possible to demonstrate EV-71 infection. Seven of the 24 children infected with EV-71 exhibited residual motor deficiency when examined 6 months after the disease onset. The relevance of these results for the Plan for Global Eradication of Wild Poliovirus is discussed, as well as the need to increase knowledge about the behaviour of this virus and its possible association with AND.

Antigen specificity of CD4 T cell response in the central nervous system of mice infected with mouse hepatitis virus

Previously, we showed that the transmembrane (M) and surface (S) glycoproteins were recognized by splenic CD4 T lymphocytes harvested from mice infected intraperitoneally with mouse hepatitis virus, strain JHM (MHV-JHM), whereas only the S protein was recognized by splenocytes derived from mice with MHV-induced chronic demyelination. From these results, it could not be determined which proteins were recognized by T cells localized in the infected central nervous system (CNS). Herein, we show that CD4 T cells responding to both the M and S proteins can be detected in the CNS of mice with either acute encephalitis or the chronic demyelinating disease. As part of these analyses, two CD4 T cell epitope regions encompassing residues 328-347 and 358-377 within the S protein were identified. Both epitopes, as well as a previously identified M-specific epitope, were recognized by the CNS-derived lymphocytes. Finally, viral RNA harvested from mice with chronic demyelination was analyzed for mutations in the S specific CD4 T cell epitopes since changes resulting in escape from CD8 T cell surveillance were previously identified in these samples. A mutation in epitope region S(328-347) (ala to thr at position 337) was detected in a minority of samples but this change did not abrogate recognition of the epitope and therefore was unlikely to contribute to virus persistence. In conclusion, these studies identify epitopes recognized by MHV-specific CD4 T cells in the infected CNS and show that these cells are preferentially located at the site of infection in mice with clinical disease.

Development of chemiluminescent probe hybridization, RT-PCR and nucleic acid cycle sequencing assays of Sabin type 3 isolates to identify base pair 472 Sabin type 3 mutants associated with vaccine associated paralytic poliomyelitis

Sabin type 3 polio vaccine virus is the most common cause of poliovaccine associated paralytic poliomyelitis. Vaccine associated paralytic poliomyelitis cases have been associated with Sabin type 3 revertants containing a single U to C substitution at bp 472 of Sabin type 3. A rapid method of identification of Sabin type 3 bp 472 mutants is described. An enterovirus group-specific probe for use in a chemiluminescent dot blot hybridization assay was developed to identify enterovirus positive viral lysates. A reverse transcription-polymerase chain reaction (RT-PCR) assay producing a 319 bp PCR product containing the Sabin type 3 bp 472 mutation site was then employed to identify Sabin type 3 isolates. Chemiluminescent nucleic acid cycle sequencing of the purified 319 bp PCR product was then employed to identify nucleic acid sequences at bp 472. The enterovirus group probe hybridization procedure and isolation of the Sabin type 3 PCR product were highly sensitive and specific; nucleic acid cycle sequencing corresponded to the known sequence of stock Sabin type 3 isolates. These methods will be used to identify the Sabin type 3 reversion rate from sequential stool samples of infants obtained after the first and second doses of oral poliovirus vaccine.

Detection and rapid differentiation of human enteroviruses following genomic amplification

By employing a nested PCR (n-PCR) with specific primers derived from the 5' nontranslated and consensus region of the human enterovirus genome, we detected enterovirus RNA from 32 different serotypes of prototypic strains. A specific 297-bp fragment was amplified by this method from all of these strains. Not only was the method highly sensitive, detecting enterovirus RNA extracted from 0.01 50% tissue culture infective dose/50 microl (which is more sensitive than our current routine method of enterovirus diagnosis, based on the virus isolation and serotypic neutralization), but it was also relatively rapid. By using this technology, we also detected enterovirus RNA in uncultured specimens (including throat swabs and stools) from patients with respiratory illness and acute flaccid paralysis syndrome. This method enabled us to rapidly and directly distinguish enterovirus-infected specimens from nonenterovirus specimens in laboratory diagnosis. Furthermore, restriction fragment length polymorphism was assessed as an alternative means of differentiating various serotypes of prototypical enteroviruses. Fourteen of 16 human enterovirus-infected specimens exhibited restriction patterns identical to those of the corresponding prototypes.