Factors Contributing to the Emergence of Escherichia coli O157 in Africa

Paul Effler, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; Margaretha Isaäcson, Lorraine Arntzen, South African Institute for Medical Research, Johannesburg, South Africa; Rosemary Heenan, GOAL, Dublin, Ireland; Paul Canter, Ubombo Sugar Limited, Big Bend, Swaziland; Timothy Barrett, Lisa Lee, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; Clifford Mambo, Ubombo Sugar Limited, Big Bend, Swaziland; William Levine, Akbar Zaidi, Patricia M. Griffin, Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Disclosures

Emerging Infectious Diseases. 2001;7(5) 

In This Article

Abstract and Introduction

In 1992, a large outbreak of bloody diarrhea caused by Escherichia coli O157 infections occurred in southern Africa. In Swaziland, 40,912 physician visits for diarrhea in persons ages ≥5 years were reported during October through November 1992. This was a sevenfold increase over the same period during 1990-91. The attack rate was 42% among 778 residents we surveyed. Female gender and consuming beef and untreated water were significant risks for illness. E. coli O157:NM was recovered from seven affected foci in Swaziland and South Africa; 27 of 31 patient and environmental isolates had indistinguishable pulsed-field gel electrophoresis patterns. Compared with previous years, a fivefold increase in cattle deaths occurred in October 1992. The first heavy rains fell that same month (36 mm), following 3 months of drought. Drought, carriage of E. coli O157 by cattle, and heavy rains with contamination of surface water appear to be important factors contributing to this outbreak.

Early in November 1992, physicians arriving for duty at a small hospital on a sugar plantation in Swaziland found >100 persons sprawled on the ground in front of the casualty department. Many had bloody diarrhea, and almost all were suffering severe abdominal pains. The next day the number of patients with the dysenteric illness nearly doubled, yet stool specimens sent to local laboratories did not yield common parasitic or bacterial pathogens, including Shigella spp. With the etiologic agent still unknown into the second week of the outbreak, specimens were forwarded to a reference laboratory in South Africa, where a surprising discovery was made: Escherichia coli O157 had emerged in Africa[1].

An outbreak of E. coli O157 infections was heretofore unheard of in Africa, or for that matter, anywhere in the developing world. E. coli O157 had been isolated only once before in southern Africa, from an elderly man undergoing surgery for lower gastrointestinal bleeding in Johannesburg in 1990[2]. We present a comprehensive account of a 1992 regional outbreak in Africa, perhaps the largest E. coli O157 outbreak ever reported.

The Kingdom of Swaziland occupies 17,360 km2 in southern Africa; 62% of the surface area is pastureland used primarily for cattle. The estimated human population in 1992 was 850,000. The sugar plantation referred to in this report is located in the Lubombo District, a lowland area that shares borders with Mozambique and South Africa (Figure 1). The plantation irrigates its extensive cane fields with water drawn from the nearby Usutu River. Twenty villages dispersed across the plantation housed approximately 5,000 workers and dependents. Standpipes with treated potable water and other pipes carrying untreated surface water were located in most villages. Plantation workers were provided with a weekly ration of beef obtained from local abattoirs.

Figure 1. Map of the area affected by an outbreak of diarrheal illness in 1992.a

aPulsed-field gel electrophoresis of 31 of the Escherichia coli O157:NM isolates from six locations identified three distinct patterns, designated A, B and C; the locations where these isolates were obtained are indicated on the map by the corresponding letter. Not shown on the map is Empangeni, South Africa, located approximately 200 km south of Swaziland border, where E. coli O157 was also recovered. The Usutu River is also called the Lusutfu River.

When the outbreak occurred, two refugee settlements, Ndzevane (population 7,700) and Malindza (population 11,900), were located 19 km and 60 km, respectively, from the plantation. Refugees and Swazi nationals residing locally received health care at settlement clinics. Jeppe's Reef, Pongola, Empangeni, Piet Retief, and Ermelo are towns and villages in nearby South Africa.

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