Study estimates global burden of listeriosis

‘Urgent efforts’ needed to fill Listeria data gap in developing countries: WHO study

By Rachel Arthur contact

- Last updated on GMT

Listeriosis is caused by the bacterium Listeria monocytogenes
Listeriosis is caused by the bacterium Listeria monocytogenes

Related tags: Listeriosis, Immune system

Listeriosis caused 23,150 illnesses, 5,463 deaths, and 172,823 disability-adjusted life-years in 2010, according to estimates in a study in The Lancet Infectious Diseases journal. 

However, the World Health Organisation (WHO) funded study - which claims to be the first to quantify the global burden of listeriosis - warns there is still ‘great uncertainty’ of the real impact.

The authors found a lack of data for 85 countries (which accounts for almost half the 2010 global population) and say that information from these regions is urgently needed.

A cause of major foodborne outbreaks

Since being recognised as a foodborne pathogen in the 1980s, Listeriosis has been identified as a cause of major foodborne outbreaks.

In healthy people, L monocytogenes can cause febrile gastroenteritis (fever and diarrhea/vomiting), which is usually mild and self-limiting. However, Listeriosis mainly occurs in at-risk groups, such as pregnant women, the elderly, and immunocompromised people.

In patients with impaired cell-mediated immunity, listeriosis can lead to severe illnesses, including severe sepsis, meningitis, or encephalitis, with lifelong consequences or death.

Infection during pregnancy can result in spontaneous abortions or stillbirths, and preterm birth is also a common consequence of listeriosis.

25.9% of non-perinatal cases result in death

The proportion of perinatal cases (the period close to or soon after birth) was 20.7%. Non-perinatal cases accounted for 79·3%.

Septicaemia was the most common outcome in perinatal cases, occurring in 30·7% of infected neonates,” ​said Charline Maertens de Noordhout, one of the researchers. “In total, 15·2% of neonates with listeriosis developed CNS [central nervous system] infections, of whom 43·8% showed neurological sequelae.

“9·2% of all perinatal cases resulted in neonatal deaths (among livebirths) and 5·7% resulted in stillbirths, for an overall case fatality of 14·9%.

In non-perinatal cases the elderly were most affected, with 71% of cases occurring in those over 55.

“Of all non-perinatal listeriosis cases, 61·6% resulted in septicaemia and 30·7% resulted in CNS infections. Of the non-perinatal cases affected by CNS infection, 13·7% developed neurological sequelae. In total, 25·9% of the non-perinatal cases resulted in death.”

Across WHO regions, the highest listeriosis rate was in the AMRO B subregion (mainly South American countries) and the lowest in EURO B (eastern Europe, western and central Asia).

“Our meta-analysis provides the first estimates of the global burden of listeriosis, and enables the relative burden of listeriosis to be put in perspective,” ​said Maertens de Noordhout.

“Compared with other foodborne pathogens, L monocytogenes causes fewer infections than do non-typhoidal salmonella , Salmonella Typhi or Toxoplasma gondii related to congenital cases; and  L monocytogenes causes a similar number of infections to Echinococcus multilocularis. L monocytogenes also caused fewer deaths than did STyphi or non-typhoidal salmonella.

“The number of DALYs [disability-adjusted life-years] due to listeriosis was lower than that due to congenital toxoplasmosis, but accords with DALYs due to echinococcosis. However, unlike these other diseases, listeriosis is mainly foodborne and is a major problem for the food industry, because it is difficult to control in the production environment.”

Lack of data for low-income countries

The study searched journals, national surveillance data, and contacted health ministries for incidence data. It then constructed a disease model based on the data.

The study says it has uncovered significant gaps in listeriosis data. Most importantly, it was unable to find useful incidence data for a number of African, Middle Eastern, and south Asian countries. No data was available for 85 countries, which accounted for a population of 3, 320, 865, 627 (48% of the global population in 2010).

The study could only find data from high-income and middle-income regions, and said certain assumptions had to be made to produce global estimations. These assumptions could not be checked against observed data and so ‘might greatly affect the final results.’

“This study is the first attempt to quantify the global burden of listeriosis​ , and will enable listeriosis to be included in international prioritisation exercises. Nevertheless, because of the scarce data on listeriosis incidence, great uncertainty remains about the real effect of listeriosis worldwide,” ​said Maertens de Noordhout

“We encourage further studies, especially in the AFRO [Africa], EMRO [Middle East and North Africa], and SEARO [southern Asia] WHO regions, to increase efforts to generate and share local data about listeriosis incidence. As additional data become available, an update of our analysis should be done.”

Third most costly foodborne pathogen

Listeriosis often results in admission to intensive care units, and the study notes L monocytogenes​ was the third most costly foodborne pathogen in the USA per case in 2010, after Clostridium botulinum​ and Vibrio vulnificus​.

Unlike most other foodborne pathogens, L monocytogenes can grow in food with fairly low moisture content and high salt concentration,” ​said ​Maertens de Noordhout.

“Most importantly, L monocytogenes grows at refrigeration temperatures, by contrast with many other foodborne pathogens. This ability to persist and multiply in the food environment makes L monocytogenes especially difficult to control.”

Source: The Lancet Infectious Diseases 

September 15 2014, DOI: 10.1016/S1473-3099(14)70870-9

‘The global burden of listeriosis: a systematic review and meta-analysis’

C. Maertens de Noordhout, B. Devleesschauwer, F.J. Angulo, J. Haagsma, M. Kirk, A. Havelaar, N. Speybroeck.

Related topics: Food Safety & Quality

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