Peter W. Robertson

Determination and importance of varicella immune status of nursing staff in a children's hospital

A survey of nurses at the Prince of Wales Childrens Hospital was conducted to determine the prevalence of immunity to varicella-zoster virus (VZ) as defined by enzyme immunoassay (EIA), and to establish the value of history as a predictor of immunity. Of the 209 nurses surveyed, 51% could recall suffering VZ infection, and with a single exception, all of this group were immune. However, despite a 95% prevalence of immunity among all nurses, 46% of those found to be immune by EIA could not recollect having VZ infection. In the event of a hospital VZ outbreak, the latter group, without serological testing, would thus need to be regarded as susceptible, and this would create a major logistical problem in staffing the affected areas. We suggest, to minimize this cause of disruption to services, that all paediatric staff with patient contact should be asked at the time of recruitment if they recall suffering VZ infection. Those who give a positive response may be considered immune, but all other staff should have their immune status assessed by EIA at the earliest opportunity.

Assessing detection probabilities for the endangered growling grass frog (Litoria raniformis) in southern Victoria

Assessment of the efficacy of survey techniques for determining species occurrence is crucial for the validation of wildlife survey data. We analysed repeated site-survey data for adults and larvae of the growling grass frog (Litoria raniformis) in order to estimate probabilities of detection for the species using alternative survey techniques. The estimated probability of detecting adults of L. raniformis at occupied sites using diurnal searches was much less than 1.0 (0.107; 95% credible interval: 0.045, 0.192). The estimated probability of detecting adults using nocturnal spotlight searches was considerably higher, but still less than 1.0 (0.696; 95% credible interval: 0.585, 0.796). These results indicate that nocturnal searches are a much more efficient and reliable means of detecting the presence of adult L. raniformis than diurnal searches, but detection using either technique is less than certain. The probability of detecting tadpoles of L. raniformis using either funnel-trapping or dip-netting techniques was estimated at 0.350 (95% credible interval: 0.151, 0.567). Together, these results indicate that reliance on single-site visits during surveys for this species is likely to result in severe under-estimation of the proportion of sites that are actually occupied. We urge other workers to use repeated site-survey data and appropriate methods of data analysis to assess and report probabilities of detection when documenting the results of wildlife surveys.

A Laboratory-Based Evaluation of Four Rapid Point-of-Care Tests for Syphilis

Background Syphilis point-of-care tests may reduce morbidity and ongoing transmission by increasing the proportion of people rapidly treated. Syphilis stage and co-infection with HIV may influence test performance. We evaluated four commercially available syphilis point-of-care devices in a head-to-head comparison using sera from laboratories in Australia. Methods Point-of-care tests were evaluated using sera stored at Sydney and Melbourne laboratories. Sensitivity and specificity were calculated by standard methods, comparing point-of-care results to treponemal immunoassay (IA) reference test results. Additional analyses by clinical syphilis stage, HIV status, and non-treponemal antibody titre were performed. Non-overlapping 95% confidence intervals (CI) were considered statistically significant differences in estimates. Results In total 1203 specimens were tested (736 IA-reactive, 467 IA-nonreactive). Point-of-care test sensitivities were: Determine 97.3%(95%CI:95.8–98.3), Onsite 92.5%(90.3–94.3), DPP 89.8%(87.3–91.9) and Bioline 87.8%(85.1–90.0). Specificities were: Determine 96.4%(94.1–97.8), Onsite 92.5%(90.3–94.3), DPP 98.3%(96.5–99.2), and Bioline 98.5%(96.8–99.3). Sensitivity of the Determine test was 100% for primary and 100% for secondary syphilis. The three other tests had reduced sensitivity among primary (80.4–90.2%) compared to secondary syphilis (94.3–98.6%). No significant differences in sensitivity were observed by HIV status. Test sensitivities were significantly higher among high-RPR titre (RPR≥8) (range: 94.6–99.5%) than RPR non-reactive infections (range: 76.3–92.9%). Conclusions The Determine test had the highest sensitivity overall. All tests were most sensitive among high-RPR titre infections. Point-of-care tests have a role in syphilis control programs however in developed countries with established laboratory infrastructures, the lower sensitivities of some tests observed in primary syphilis suggest these would need to be supplemented with additional tests among populations where syphilis incidence is high to avoid missing early syphilis cases.

Syphilis in New South Wales (Australia) prisons

This paper describes the prevalence of, and risk factors for, exposure to syphilis in a random sample of male and female prisoners. We found that only 2% of male and 1% of female prison inmates in New South Wales (NSW) had confirmed evidence of untreated syphilis, and none appeared to be in an infectious phase. In the multivariate analysis, indigenous ethnicity remained the most potent predictor for confirmed syphilis (either past or present). There was some evidence to suggest that syphilis among indigenous prisoners may be associated with limited access to health services outside prison. The epidemiology of syphilis reflects that of the general community suggesting that prisons could be used as sentinel sites to help evaluate the effectiveness of STD prevention and control strategies.

Concurrent summer influenza and pertussis outbreaks in a nursing home in Sydney, Australia.

OBJECTIVE To report on the investigation of a summer outbreak of acute respiratory illness among residents of a Sydney nursing home. DESIGN An epidemiologic and microbiological investigation of the resident cohort at the time of the outbreak and medical record review 5 months later. SETTING A nursing home located in Sydney, Australia, during February to July 1999. PATIENTS The cohort of residents present in the nursing home at the time of the outbreak. INTERVENTIONS Public health interventions included recommendations regarding hygiene, cohorting of residents and staff, closure to further admissions, and prompt reporting of illness; and virologic and serologic studies of residents. RESULTS Of the 69 residents (mean age, 85.1 years), 35 fulfilled the case definition of acute respiratory illness. Influenza A infection was confirmed in 19 residents, and phylogenetic analysis of the resulting isolate, designated H3N2 A/Sydney/203/99, showed that it differed from strains isolated in eastern Australia during the same period. Serologic evidence of Bordetella infection was also found in 10 residents; however, stratified epidemiologic analysis pointed to influenza A as the cause of illness. CONCLUSIONS The investigation revealed an unusual summer outbreak of influenza A concurrent with subclinical pertussis infection. Surveillance of acute respiratory illness in nursing homes throughout the year, rather than solely during epidemic periods, in combination with appropriate public health laboratory support, would allow initiation of a timely public health response to outbreaks of acute respiratory illness in this setting.

Microhabitat preferences of the endangered Growling Grass Frog * Litoria raniformis in southern Victoria

We examined nocturnal microhabitat preferences of the endangered Growling Grass Frog Litoria raniformis in lotic and lentic environments in southern Victoria, Australia. Data were obtained during surveys of six wetland sites during the summer of 2003. At all sites the observed distribution of frogs amongst microhabitat categories differed from their availability, as assessed by sampling of random points. Frogs were located most often on bare soil, bare rock or leaf litter when on land, and on floating, submergent and emergent vegetation in aquatic situations. Non-metric multidimensional scaling and analysis of similarities (ANOSIM) were used to compare the structural attributes of microhabitats used by L. raniformis to those of random points. In both the riparian and aquatic zones of the study sites, microhabitats used by these frogs differed from random points in their degree of vertical structural complexity. Whilst our data may be biased by the observability of frogs in different microhabitats, this st...

Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

Several outbreaks of hepatitis A in men who have sex with men (MSM) were reported in the 1980s and 1990s in Australia and other countries. An effective hepatitis A virus (HAV) vaccine has been available in Australia since 1994 and is recommended for high-risk groups including MSM. No outbreaks of hepatitis A in Australian MSM have been reported since 1996. In this study, we aimed to estimate HAV transmissibility in MSM populations in order to inform targets for vaccine coverage in such populations. We used mathematical models of HAV transmission in a MSM population to estimate the basic reproduction number (R 0) and the probability of an HAV epidemic occurring as a function of the immune proportion. We estimated a plausible range for R 0 of 1·71-3·67 for HAV in MSM and that sustained epidemics cannot occur once the proportion immune to HAV is greater than ~70%. To our knowledge this is the first estimate of R 0 and the critical population immunity threshold for HAV transmission in MSM. As HAV is no longer endemic in Australia or in most other developed countries, vaccination is the only means of maintaining population immunity >70%. Our findings provide impetus to promote HAV vaccination in high-risk groups such as MSM.

Investigation of isolated positive syphilis enzyme immunoassay (ICE Murex) results

This study was conducted to determine the significance of an isolated positive (where all other syphilis serology is negative) syphilis enzyme immunoassay (EIA) test (ICE syphilis: Murex Diagnostics) in a sexual health clinic population. There were significantly greater numbers of isolated positive syphilis EIA tests at Sydney Sexual Health Centre (SSHC) (22/5478) compared to lower risk populations; Southeastern Sydney antenatal clinics (1/11560, P<0.01) and Sydney Childrens Hospital (0/3550, P<0.01). We conducted a case control study comparing the cases at SSHC with two control groups drawn from the clinic population. A manual review of the case medical records searched for a history of suggested syphilis. Within the 22 cases, 32% had clinical grounds for suspecting that the EIA test signified syphilis. Men reporting homosexual contact in the past 12 months significantly distinguished cases from controls who tested negative for syphilis (OR=6.06). An isolated positive EIA test should prompt further investigation for syphilis, past or present.

An Evaluation of a Novel Dual Treponemal/Nontreponemal Point-of-Care Test for Syphilis as a Tool to Distinguish Active From Past Treated Infection

BACKGROUND Most syphilis point-of-care (POC) tests detect treponemal antibodies, which persist after successful treatment. Subsequent POC tests are positive, despite no active infection, and can lead to unnecessary treatment. We evaluated a new POC test, incorporating a nontreponemal component, to distinguish active from past infection. METHODS Sera stored at 2 Australian laboratories were tested with DPP Screen and Confirm Assay. Treponemal and nontreponemal test lines were compared to corresponding conventional treponemal and nontreponemal reference test results: immunoassays and rapid plasma reagin (RPR), respectively, with RPR quantification by endpoint titration. POC test outcome concordance with conventional test results was assessed according to serological and clinical categories. RESULTS Among 1005 serum samples tested, DPP treponemal line sensitivity was 89.8% (95% confidence interval [CI], 87.3%-91.9%) and specificity was 99.3% (95% CI, 97.0%-99.9%). DPP nontreponemal line sensitivity was 94.2% (95% CI, 91.8%-96.0%) and specificity was 62.2% (95% CI, 57.5%-66.6%). DPP test outcome (pair of test lines) was concordant with both reference test results for 94.3% of 404 high-titer infections, 90.1% of 121 low-titer infections, 27.5% of 211 past/treated infections, and 78.1% of 242 infections classified as not syphilis. Among 211 past/treated infections, 49.8% were incorrectly identified as active infection and a further 22.8% as not syphilis. CONCLUSIONS DPP test use would result in identification of >93% of active syphilis infections, whereas just over half of past infections would be diagnosed as past or not syphilis, avoiding unnecessary treatment compared with other POC tests. This may be at the expense of missing some active infections; thus, its potential benefits will depend on the prevalence of past vs active infection in a population.

Improving diagnosis of primary cytomegalovirus infection in pregnant women using immunoblots.

Human cytomegalovirus (CMV) is the most common infectious cause of mental disability in newborns of developed countries. Transmission of CMV from mother to baby is more frequent in maternal primary infection, although CMV reactivation causes more congenital infections overall. Current diagnostic tests for distinguishing primary and reactivation CMV have problems with interpretation and immunoblots may assist with diagnosis. Sera from 60 pregnant women were analyzed using conventional serology in parallel with a commercial immunoblot assay (using Recomblot, Mikrogen Diagnostik). Comparison of detection of CMV IgG, IgM, IgG avidity in maternal primary infection showed the immunoblot relative to conventional serology had sensitivity and specificity of 100% for IgG identification. The detection of IgM on immunoblot showed sensitivity of 75%, specificity of 62.5%, positive predictive value (PPV) of 81.8% and negative predictive value (NPV) of 52.6%. The immunoblot IgG avidity assay had sensitivity of 94.1%, with a PPV of 100% when identifying low avidity serum samples, and sensitivity of 100% with a PPV of 97.1% for high avidity serum samples. Overall agreement between conventional serology (IgM, IgG avidity) and immunoblot (IgM, IgG avidity) for detection of primary CMV infection was 65%. Although the immunoblot is effective in detecting IgG and determining IgG avidity, it showed no significant benefits in performance or utility as a first line diagnostic technique for IgM or primary CMV infection in pregnant women. J. Med. Virol. 85:315–319, 2013.