Universal immunization: the diphtheria control strategy of choice in the Republic of Tajikistan, 1993-1997

Bacterial infection during wars, conflicts and post-natural disasters in Asia and the Middle East: a narrative review

Introduction: Bacterial infections resulting from wars and natural disasters represent a major public health problem. Over the past 50 years, Asia and the Middle East have suffered several wars. Moreover, East-Asian countries are considered the most natural disaster-prone countries in the world.Areas covered: This review focuses on bacterial infection occurring during wars and after natural disasters, among refugees, wounded citizens and soldiers as well as the prevention and control measures that must be taken.Expert opinion: During wars, refugees and soldiers represent the two main sources of bacterial infections. Refugees coming from countries with a high prevalence of antimicrobial resistance can spread these pathogens to their final destination. In addition, these refugees living in inadequate shelters can contribute to the spread of bacterial infections. Moreover, some factors including the presence of fixed imported fragments; environmental contamination and nosocomial transmissions, play a key role in the dissemination of bacteria among soldiers. As for natural disasters, several factors are associated with increased bacterial transmissions such as the displacement of large numbers of people into over-crowded shelters, high exposure to disease vectors, lack of water and sanitation. Here, we carry out a systematic review of the bacterial infections that follow these two phenomena.

Spatial Distribution and Trends of Waterborne Diseases in Tashkent Province

Introduction

The cumulative effect of limited investment in public water systems, inadequate public health infrastructure, and gaps in infectious disease prevention increased the incidence of waterborne diseases in Uzbekistan. The objectives of this study were: (1) to spatially analyze the distribution of the diseases in Tashkent Province, (2) to identify the intensity of spatial trends in the province, (3) to identify urban-rural characteristics of the disease distribution, and (4) to identify the differences in disease incidence between pediatric and adult populations of the province.

Methods

Data on four major waterborne diseases and socio-demographics factors were collected in Tashkent Province from 2011 to 2014. Descriptive epidemiological methods and spatial-temporal methods were used to investigate the distribution and trends, and to identify waterborne diseases hotspots and vulnerable population groups in the province.

Results

Hepatitis A and enterobiasis had a high incidence in most of Tashkent Province, with higher incidences in the eastern and western districts. Residents of rural areas, including children, were found to be more vulnerable to the waterborne diseases compared to other populations living in the province.

Conclusions

This pilot study calls for more scientific investigations of waterborne diseases and their effect on public health in the region, which could facilitate targeted public health interventions in vulnerable regions of Uzbekistan.

Determination of the presence of diphtheria toxin in the myocardial tissue of rabbits and a female subject by using an immunofluorescent antibody method

BACKGROUND

Clinical diagnosis of diphtheria is often difficult, in particular in countries where the disease is rarely observed, such as Turkey. In 2011, after 12 years of no recorded diphtheria cases in Turkey, a 34-year-old woman was diagnosed with diphtheria; she later died of myocarditis. In this study, we aimed to demonstrate the diagnostic potential of an immunofluorescent antibody method to determine the presence of diphtheria toxin (DT) in the myocardial cells of DT-injected rabbits and the female subject.

METHODS

We randomly divided rabbits into two groups: a control group and a DT-injected group. Diphtheria intoxication was simulated in the rabbits by intravenous injection of DT. The myocardium of the rabbits and the female subject were harvested for histopathologic and immunofluorescence examination. A mouse monoclonal anti-DT antibody was used for the immunofluorescent antibody method.

RESULTS

The presence of DT in the myocardial cells of both the rabbits and the female subject was visualized using the immunofluorescent method.

CONCLUSIONS

Laboratory diagnosis of diphtheria is challenging because of non-toxigenic C. diphtheriae strains and/or the dysfunction of DT. However, visualizing the presence of DT in the myocardial tissue may act as an indicator of biologically active DT. We validated that an immunofluorescent method, which utilizes a monoclonal anti-DT (A-subunit specific) antibody, is a useful diagnostic tool to determine the presence of DT in the myocardium of rabbits and human.

Seroepidemiology of diphtheria and tetanus among children and young adults in Tajikistan: nationwide population-based survey, 2010

BACKGROUND

Tajikistan had a major diphtheria outbreak (≈ 10,000 cases) in the 1990 s, which was controlled after nationwide immunization campaigns with diphtheria-tetanus toxoid in 1995 and 1996. Since 2000, only 52 diphtheria cases have been reported. However, in coverage surveys conducted in 2000 and 2005, diphtheria-tetanus-pertussis vaccine coverage was lower than administratively reported estimates raising concerns about potential immunity gaps. To further assess population immunity to diphtheria in Tajikistan, diphtheria antibody testing was included in a large-scale nationwide serosurvey for vaccine-preventable diseases conducted in connection with a poliomyelitis outbreak in 2010. In addition, the serosurvey provided an opportunity to assess population immunity to tetanus.

METHODS

Residents of all regions of Tajikistan aged 1-24 years were included in the serosurvey implemented during September-October 2010. Participants were selected through stratified cluster sampling. Specimens were tested for diphtheria antibodies using a Vero cell neutralization assay and for tetanus antibodies using an anti-tetanus IgG ELISA. Antibody concentrations ≥ 0.1 IU/mL were considered seropositive.

RESULTS

Overall, 51.4% (95% CI, 47.1%-55.6%) of participants were seropositive for diphtheria and 78.9% (95% CI, 74.7%-82.5%) were seropositive for tetanus. The lowest percentages of seropositivity for both diseases were observed among persons aged 10-19 years: diphtheria seropositivity was 37.1% (95% CI, 31.0%-43.7%) among 10-14 year-olds, and 35.3% (95% CI, 29.9%-41.1%) among 15-19 year-olds; tetanus seropositivity in respective age groups was 65.3% (95% CI, 58.4%-71.6%) and 70.1% (95% CI, 64.5%-75.2%).

CONCLUSIONS

Population immunity for diphtheria in Tajikistan is low, particularly among 10-19 year-olds. Population immunity to tetanus is generally higher than for diphtheria, but is suboptimal among 10-19 year-olds. These findings highlight the need to improve routine immunization service delivery, and support a one-time supplementary immunization campaign with diphtheria-tetanus toxoid among birth cohorts aged 1-19 years in 2010 (3-21 years in 2012) to close immunity gaps and prevent diphtheria outbreaks.

Acute viral hepatitis morbidity and mortality associated with hepatitis E virus infection: Uzbekistan surveillance data

Background

In Uzbekistan, routine serologic testing has not been available to differentiate etiologies of acute viral hepatitis (AVH). To determine the age groups most affected by hepatitis E virus (HEV) during documented AVH epidemics, trends in AVH-associated mortality rate (MR) per 100,000 over a 15-year period and reported incidence of AVH over a 35-year period were examined.

Methods

Reported AVH incidence data from 1971 to 2005 and AVH-associated mortality data from 1981 to 1995 were examined. Serologic markers for infection with hepatitis viruses A, B, D, and E were determined from a sample of hospitalized patients with AVH from an epidemic period (1987) and from a sample of pregnant women with AVH from a non-epidemic period (1992).

Results

Two multi-year AVH outbreaks were identified: one during 1975–1976, and one during 1985–1987. During 1985–1987, AVH-associated MRs were 12.3–17.8 per 100,000 for the general population. Highest AVH-associated MRs occurred among children in the first 3 years of life (40–190 per 100,000) and among women aged 20–29 (15–21 per 100,000). During 1988–1995 when reported AVH morbidity was much lower in the general population, AVH-associated MRs were markedly lower among these same age groups. In 1988, AVH-associated MRs were higher in rural (21 per 100,000) than in urban (8 per 100,000) populations (RR 2.6; 95% CI 1.16–5.93; p < 0.05). Serologic evidence of acute HEV infection was found in 280 of 396 (71%) patients with AVH in 1987 and 12 of 99 (12%) pregnant patients with AVH in 1992.

Conclusion

In the absence of the availability of confirmatory testing, inferences regarding probable hepatitis epidemic etiologies can sometimes be made using surveillance data, comparing AVH incidence with AVH-associated mortality with an eye to population-based viral hepatitis control measures. Data presented here implicate HEV as the probable etiology of high mortality observed in pregnant women and in children less than 3 years of age in Uzbekistan during 1985–1987. High mortality among pregnant women but not among children less than 3 years has been observed in previous descriptions of epidemic hepatitis E. The high mortality among younger children observed in an AVH outbreak associated with hepatitis E merits corroboration in future outbreaks.

Impact of infectious diseases on war

Wartime epidemics of infectious diseases have decimated the fighting strength of armies, caused the suspension and cancellation of military operations, and brought havoc to the civil populations of belligerent and nonbelligerent states. This article summarizes the principal factors that have contributed to the spread of infectious diseases in past wars and reviews the associated demographic losses in military and civil populations. Drawing on the detailed epidemiologic records for the United States Army, case studies of the spread of infectious diseases in relation to military mobilization are presented for the American Civil War, Spanish-American War,and World War I. The article concludes with a brief overview of infectious disease activity in high- and low-intensity conflicts of the late twentieth and early twenty-first centuries.

Diphtheria remains a threat to health in the developing world: an overview

Changes in the epidemiology of diphtheria are occurring worldwide. A large proportion of adults in many industrialized and developing countries are now susceptible to diphtheria. Vaccine-induced immunity wanes over time unless periodic booster is given or exposure to toxigenic Corynebacterium diphtheriae occurs. Immunity gap in adults coupled with large numbers of susceptible children creates the potential for new extensive epidemics. Epidemic emergencies may not be long in coming in countries experiencing rapid industrialization or undergoing sociopolitical instability where many of the factors thought to be important in producing epidemic such as mass population movements and difficult hygienic and economic conditions are present. The continuous circulation of toxigenic C. diphtheriae emphasizes the need to be aware of epidemiological features, clinical signs, and symptoms of diphtheria in vaccine era so that cases can be promptly diagnosed and treated, and further public health measures can be taken to contain this serious disease. This overview focused on worldwide data obtained from diphtheria with particular emphasis to main factors leading to recent epidemics, new clinical forms of C. diphtheriae infections, expression of virulence factors, other than toxin production, control strategies, and laboratory diagnosis procedures.

Endemic infectious diseases of Afghanistan

The current crisis in Afghanistan has resulted in an influx of Western military personnel, peacekeepers, humanitarian workers, and journalists. At the same time, unprecedented numbers of internally displaced persons and refugees have overwhelmed much of the already fragile infrastructure, setting the stage for outbreaks of infectious diseases among both foreigners and local populations. This review surveys the literature concerning the infectious diseases of Afghanistan and south-central Asia, with particular emphasis on diseases not typically seen in the Western world.

Successful control of epidemic diphtheria in the states of the Former Union of Soviet Socialist Republics: lessons learned

Epidemic diphtheria reemerged in the Russian Federation in 1990 and spread to all Newly Independent States (NIS) and Baltic States by the end of 1994. Factors contributing to the epidemic included increased susceptibility of both children and adults, socioeconomic instability, population movement, deteriorating health infrastructure, initial shortages of vaccine, and delays in implementing control measures. In 1995, aggressive control strategies were implemented, and since then, all affected countries have reported decreases of diphtheria; however, continued efforts by national health authorities and international assistance are still needed. The legacy of this epidemic includes a reexamination of the global diphtheria control strategy, new laboratory techniques for diphtheria diagnosis and analysis, and a model for future public health emergencies in the successful collaboration of multiple international partners. The reemergence of diphtheria warns of an immediate threat of other epidemics in the NIS and Baltic States and a longer-term potential for the reemergence of vaccine-preventable diseases elsewhere. Continued investment in improved vaccines, control strategies, training, and laboratory techniques is needed.

Diphtheria surveillance and control in the Former Soviet Union and the Newly Independent States

The Newly Independent States (NIS) inherited a common approach to diphtheria control from the Soviet Union and maintained a centralized system of surveillance and control managed by Soviet-trained epidemiologists with a shared professional culture. This system had controlled a diphtheria resurgence in the 1980s. In response to the epidemic of the 1990s, NIS health authorities responded with a set of control measures based on the Soviet-era experience. These measures included intensified childhood vaccination, aggressive case investigation, widespread diphtheria screening in institutions, and vaccination of adults in high-risk occupation groups. These measures proved insufficient due to high levels of susceptibility among adults, excessive contraindications to childhood vaccination, and insufficient resources in many countries. After these initial delays in implementing effective measures in some countries, most of the NIS health authorities rapidly and successfully implemented mass immunization of the population against diphtheria once the strategy was adopted and sufficient vaccine was available.

Diphtheria epidemic in the Republic of Uzbekistan, 1993-1996

The Republic of Uzbekistan, like the other Newly Independent States in the 1990s, experienced epidemic diphtheria during the 1990s. The outbreak in Uzbekistan began in 1993 in southern regions that bordered areas of Tajikistan that were experiencing a very intense diphtheria epidemic. However, the Uzbek epidemic rapidly spread and threatened to involve the entire country. From 1993-1996, 1169 cases of diphtheria were reported, compared with 58 in 1990-1992. Unvaccinated or only partially vaccinated cases were more likely to have clinically severe forms of diphtheria than those who were fully vaccinated. Strong epidemiologic links with the Tajik diphtheria epidemic and the predominance of mitis biotype strains of Corynebacterium diphtheriae in Uzbekistan make it likely that the Uzbek outbreak arose independently of the predominantly biotype gravis epidemic that began in Russia. The epidemic appeared to be due to low population immunity and the large-scale reintroduction of toxigenic strains of C. diphtheriae. Several mass vaccination campaigns and general enhancement of routine immunization procedures led to control of the epidemic in 1996.

Epidemic diphtheria in the 1990s: Azerbaijan

The diphtheria epidemic in the former Soviet Union reached Azerbaijan in 1991, when 66 cases of diphtheria were reported, a number that compared with 4 cases in 1990. From 1990-1996, 2182 cases of diphtheria and 286 diphtheria fatalities (case fatality rate: 13.1%) were reported in Azerbaijan, primarily among persons 5-39 years of age. Almost 45% of cases and 61% of deaths occurred among children 5-14 years of age. The high burden of severe disease among children and young adults suggested a different pattern of preexisting immunity against diphtheria in the Azerbaijani population than was observed in the concurrent diphtheria epidemic in Russia. Because resources were limited in Azerbaijan, mass immunization of the population was carried out in stages, focusing initially on school-aged children. Mass immunization campaigns targeting children were moderately successful in stabilizing the epidemic; mass immunization campaigns targeting both adults and children were eventually needed to fully stop the epidemic.