Role of environmental poliovirus surveillance in global polio eradication and beyond.

Environmental poliovirus surveillance (ENV) means monitoring of poliovirus (PV) transmission in human populations by examining environmental specimens supposedly contaminated by human faeces. The rationale is based on the fact that PV-infected individuals, whether presenting with disease symptoms or not, shed large amounts of PV in the faeces for several weeks. As the morbidity:infection ratio of PV infection is very low, this fact contributes to the sensitivity of ENV which under optimal conditions can be better than that of the standard acute flaccid paralysis (AFP) surveillance. The World Health Organization has included ENV in the new Strategic Plan of the Global Polio Eradication Initiative for years 2010-2012 to be increasingly used in PV surveillance, supplementing AFP surveillance. In this paper we review the feasibility of using ENV to monitor wild PV and vaccine-derived PV circulation in human populations, based on global experiences in defined epidemiological situations.

The role of surveillance in polio eradication and identification of emerging viral encephalitis.

In 1988, when the World Health Assembly resolved to eradicate paralytic poliomyelitis, polio was endemic in 125 countries on 5 continents with an estimated 350,000 cases annually. By 2002, the number of countries was reduced to 7 and the number of cases by greater than 99%. Instrumental in this extraordinary progress is the timely detection and investigation of all cases of acute flaccid paralysis and the examination of stool samples in an accredited WHO Global Network laboratory. The Network consists of 124 National Poliovirus Laboratories, 15 Regional Reference Laboratories, and 7 Global Specialized Laboratories. Network Laboratories are held accountable to rigid performance standards for quality and timeliness in testing more than 60,000 stool samples annually. The Network is a hierarchical system in which polioviruses are isolated and identified in National Laboratories, differentiated as to wild or vaccine origin in Regional Reference Laboratories, and sequenced in Specialized Laboratories. Findings are promptly relayed to Regional and national program managers for immunization strategic planning, monitoring surveillance quality, and assessing eradication progress. Lessons from the Polio Laboratory Network demonstrate the value of a central coordinating body, an effective communication infrastructure, and full partnerships with peer epidemiology and medical sectors. Post-eradication polio surveillance will continue for many years. The Network legacy for other public health initiatives is access to an existing laboratory infrastructure and human resources with the proven ability to achieve technology transfer and quality laboratory performance even in resource-poor countries.

Intestinal parasites in human immunodeficiency virus infected patients

Treatment of concurrent opportunistic and non-opportunistic infections is a priority in improving quality of life in HIV infected patients in developing countries. The objective of the study was to determine the prevalence of opportunistic intestinal parasites in persons with and without HIV infection in Honduras. It was based on study of 52 HIV-positive and 48 HIV-negative persons at the Social Security Hospital in San Pedro Sula. Data sheets recording age, sex, stool parasitology, HIV serology and clinical state of HIV infection were completed for each study participant. Cryptosporidium parvum and Strongyloides stercoralis, which are intracellular or live in the mucosa, were found exclusively in persons infected with HIV. In contrast, the prevalence of the extracellular parasites Giardia lamblia, Ascaris lumbricoides and Trichuris trichiura was significantly higher in persons who were HIV-negative. It appears that infection with HIV may selectively deter the establishment of some intestinal parasites. This may be due to HIV induced enteropathy which does not favor the establishment of extracellular parasites. However, intracellular and mucosal dwelling organisms may benefit from pathological changes and reduced local immune responses which are induced by the virus which, in turn, lead to higher prevalence among HIV-infected individuals. We further postulate that the switch from a Th-1 to a predominantly Th-2 response as HIV infection progresses to AIDS may lead to an environment which is unsuitable for parasite survival (AU)

Intestinal parasitic infections in human immunodeficiency virus (HIV)-positive and HIV-negative individuals in San Pedro Sula, Honduras.

Honduras has at least five-times more human immunodeficiency virus (HIV)-infected individuals than any other country in Central America. The relationship between HIV status and the presence of intestinal parasites in this part of the world is unknown. This study presents the results from a prospective, comparative study for the presence of parasites in 52 HIV-positive and 48 HIV-negative persons in San Pedro Sula, Honduras. Infection with HIV was determined by microagglutination and confirmed by Western blot analysis. Parasites were detected in stools using formalin-ether concentration, and Kinyoun and trichrome staining. Age, sex, and clinical state of HIV infection were recorded for each study participant. Our results indicate that Cryptosporidium parvum and Strongyloides stercoralis, which are intracellular or live in the mucosa, were found exclusively in persons infected with HIV. In comparison, the prevalence of the extracellular parasites Giardia lamblia, Ascaris lumbricoides, and Trichuris trichiura was significantly higher (P < 0.05) in persons who were HIV-negative. Trichuris worms are in contact with the gut epithelium and less so with the mucosa, whereas Strongyloides lives within the gut mucosa. It is possible that changes in the gut epithelium due to HIV infection do not affect the mucosa and therefore would not affect Strongyloides. We conclude that infection with HIV may selectively deter the establishment of certain intestinal parasites. This may be due to the fact that HIV-induced enteropathy does not favor the establishment of extracellular parasites. Intracellular and mucosal dwelling organisms, however, may benefit from pathologic changes and reduced local immune responses induced by the virus, which, in turn, may lead to higher prevalence among HIV-infected individuals.

Risk factors for concordant HIV infection in heterosexual couples in Trinidad.

Risk factors for HIV infection in partners of HIV-seropositive index cases were investigated in a cross-sectional survey. Between September 1992 and April 1994 a total of 251 HIV-infected persons and 76 of their sexual partners were interviewed at the main sexually transmitted diseases (STDs) clinic in Trinidad. All participants gave signed consent and responded to a questionnaire. Sixty-four couples had risks for HIV infection through heterosexual intercourse only. However, many recruited sex partners (57/64) reported heterosexual intercourse with persons in addition to the index cases. Overall HIV concordance (both index case and partner HIV infected) was 45% in the couples. HIV concordance was not found to be related to the sexual practices within the studied unions nor to the clinical status of the index case. After allowing for confounding factors there was an increased risk for HIV concordance in couples in unions for > or = 1 year (adjusted OR 3.48; 95% CI 0.89-13.69, P = 0.055), and in those in which sex partners had a past history of genital sores (adjusted for prostitution: OR 4.50; 95% CI 1.01-20.4). Interventions targeted at reducing high-risk sexual behaviour, prostitution and cocaine use could be beneficial in reducing the spread of STDs and HIV in Trinidad.

PIP: A cross-sectional survey conducted at the main sexually transmitted disease clinic in Trinidad in 1992-94 investigated risk factors for concordant HIV infection in 251 HIV-infected persons and 76 of their sexual partners. Sexual contact with the index case was the only reported HIV risk factor for 7 partners; another 57 partners with heterosexual intercourse as the sole HIV risk factor reported intercourse with persons in addition to the index case in the preceding 5 years. Overall, HIV concordance was 45% (38% in couples with a female index case and 50% when the index case was male). HIV concordance was unrelated to either sexual practices within the studied unions (e.g., frequency of intercourse, condom use, male circumcision, sex during menstruation) or the current clinical status of the index case. After adjustment for confounding factors, there was an increased risk for HIV concordance among couples in unions for 1 or more years (adjusted odds ratio (OR), 3.48; 95% confidence interval (CI), 0.89-13.69) and those in which sex partners had a past history of genital sores (OR adjusted for prostitution, 4.50; 95% CI, 1.01-20.4). These findings suggest a need for policies to ensure that the sex partners of HIV-infected persons in Trinidad are notified, counseled, and offered HIV testing because of their elevated risk of infection.