Typhoid and Paratyphoid Fever Epidemiology in India

Introduction

The twenty-first century's onset was accompanied by growth in a range of wild and domesticated animal species acting as reservoirs and carriers of pathogens such as bacteria, parasites, and viruses. Given the continuum of animal species involved and the typically complicated natural history of pathogens, proper prevention, surveillance, and control of zoonotic infections poses a genuine public health challenge. Foodborne diseases, mad cow disease, and other newly emerged zoonoses, as well as several viral infection agents — including Ebola, Nipah, monkeypox, and Highly Pathogenic Asian Avian Influenza (H5N1) — have seriously impacted public health both directly and indirectly. With continual environmental changes, such occurrences are expected to increase in the future (Schlipkoter & Flahault, 2010).

This paper concentrates on the outbreak of paratyphoid and typhoid fever in underprivileged regions across India, discussing its contributing factors, pathophysiology, signs, symptoms, and management.

History of Typhoid and Paratyphoid Fever

In the United States, enteric fever occurs rarely. Of the approximately 500 annual cases, roughly 60% are contracted by travelers to India, South America, or Mexico. There are three stages involved in paratyphoid fever: the initial stage, characterized by high body temperature; the toxic stage, accompanied by intestinal symptoms and abdominal pain; and lastly, a protracted recovery period. For adults, these three stages may span 4–6 weeks, whereas in children the disease course may last only 10–15 days. During the second (toxic) stage, there is a one-to-ten percent chance of intestinal hemorrhage or perforation (Frey, 2006).

This disease has been identified as a well-known source of morbidity across the globe. Approximately 21.7 million typhoid cases occur globally each year, with the maximum burden borne by Central and South America, India, and sub-Saharan Africa — all regions characterized by poor sanitation and rapidly increasing populations. While limited epidemiological data exist for projecting India's actual disease burden, both population-based and hospital studies have revealed significant changes in typhoid fever occurrence (Banerjee et al., 2014).

Pathophysiology

Salmonella (S.) paratyphi (A, B, C) and Salmonella typhi are sensitive to various antibiotics in vitro (outside the organism). However, in vivo (internal) responses cannot always be predicted accurately from external susceptibility data, chiefly because these bacteria are located primarily within intracellular phagocytic cells. Since S. paratyphi and S. typhi are obligate human infections, no suitable animal models exist for testing treatment regimens.

Generally, the murine model — S. typhimurium — has been used in assessing paratyphoid and typhoid host defense systems and pathophysiology. However, this model has not been employed for evaluating treatment responses (White, 2010).

Signs, Symptoms, and Communicability

Disease onset occurs gradually and is characterized by the following:

• Constant high fever
• Malaise (general feeling of illness)
• Marked headache
• Decreased appetite
• Spleen enlargement that may result in abdominal discomfort
• Presence of a flat pink rash on the torso
• Dry cough during the initial stage of the disease
• Diarrhea or constipation — in adult patients, constipation is more common

The disease ranges in severity from mild (characterized by low-grade fever) to acute (accompanied by multiple complications). Individuals who do not receive treatment can continue to have fever for several weeks or months; an alarming 20% of these patients may succumb to disease complications during this period. With treatment, the mortality rate drops to approximately one percent. Paratyphoid symptoms are similar to those of typhoid; however, paratyphoid is typically a milder variant (Anon., n.d.).

Typhoid bacteria survive under unhygienic conditions and spread largely through the vomit and stools of carriers and typhoid patients. These bacteria are then transmitted to food, water, and drinks via insects such as houseflies, thereby contaminating food. Salmonella enteritidis paratyphi A, B, and C causes paratyphoid, which is usually milder than typhoid. The most widely occurring complications of the disease are intestinal perforation and bleeding. Polluted water is a key transmission source, as are raw vegetables cultivated on fields fertilized with sewage. The bacteria are capable of surviving for months in water and soil and undergo rapid growth in dairy products and milk (Anon., n.d.).

Epidemiological Triangle and Spread

The epidemiological triangle is a model developed by scientists to understand infections and the way they spread. It has three vertices: agent, host, and environment.

Agent: Paratyphoid and typhoid fever have been identified as key health problems in numerous developing nations. Typhoid fever's etiologic agent, Salmonella typhi (Salmonella enterica serovar Typhi), accounts for more than 20 million cases and over 200,000 deaths globally per year.

Host: After entering human hosts via contaminated food or drink, S. paratyphi and S. typhi must circumvent competing microorganisms that vie for mucosal adhesion and nutrients, evade the host's internal defense mechanisms, establish an independent niche within the mononuclear phagocytic system, and then replicate and eventually exit the host to be transmitted to another susceptible individual.

Environment: Considering the parallelism of host and pathogen factors, the balanced interaction of both with the environment is instructive. The situation in Jakarta, the Indonesian capital, illustrates how balanced host–pathogen–environment interactions lead to paratyphoid and typhoid endemicity (Ali, 2006).

S. Typhi is able to survive only in the human body. People suffering from typhoid carry these bacteria in their intestinal tract and bloodstream. Additionally, some individuals — known as "carriers" — recover from the disease while continuing to harbor and shed the bacteria. Typhoid fever may be contracted by eating food or drink handled by such a carrier, or when S. Typhi-contaminated sewage enters drinking or domestic-use water. Once consumed, the bacteria multiply and disperse through the person's bloodstream, provoking high fever and the other signs and symptoms described above (Fever, 2013).