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Research Article

Neurocysticercosis, a Persisting Health Problem in Mexico

  • Agnès Fleury mail,

    afleury@biomedicas.unam.mx

    Affiliations: Instituto Nacional de Neurología y Neurocirugía, Mexico City, México, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, México

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  • Jael Moreno García,

    Affiliation: Instituto Nacional de Neurología y Neurocirugía, Mexico City, México

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  • Paulina Valdez Aguerrebere,

    Affiliation: Instituto Nacional de Neurología y Neurocirugía, Mexico City, México

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  • María de Sayve Durán,

    Affiliation: Instituto Nacional de Neurología y Neurocirugía, Mexico City, México

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  • Paola Becerril Rodríguez,

    Affiliation: Instituto Nacional de Neurología y Neurocirugía, Mexico City, México

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  • Carlos Larralde,

    Affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, México

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  • Edda Sciutto

    Affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, México

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  • Published: August 24, 2010
  • DOI: 10.1371/journal.pntd.0000805

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Taenia solium cysticercosis: a persisting health problem in Mexico: is it debatable?

Posted by flisser on 21 Nov 2010 at 22:26 GMT

In February of this year we sent a viewpoint to PLoS NTD indicating that Taenia solium cysticercosis may not longer be a public health problem in Mexico. The manuscript has been accepted and will be published in December 2010 (1). The viewpoint was based on Mexican official and scientific data from the last 5 decades. Last August, a research article by Fleury et al that appeared in the same journal, submitted in April, had the opposite conclusion, i.e. that neurocysticercosis is a persisting health problem in Mexico (2). These authors stated that after reviewing the clinical records of patients that fulfilled the criteria for neurocysticercosis at the National Institute of Neurology and Neurosurgery (INNN) in Mexico City, no significant decrease was found in the number of cases admitted in 2004 compared to 1994. The authors also stated that the frequency of hospitalizations in the neurology service, due to this disease, was without any significant temporal trend from 1995 to 2009. In addition, the authors showed that there was no difference in the percent of cases that had multiple parasitic cysts, and that most cases in 1994 were rural while the majority of cases in 2004 were urban.
The article by Fleury et al (2) stated that all clinical records were anonymously reviewed and that the annual numbers of hospitalizations and deaths were obtained from the epidemiological service. Considering that patients with neurocysticercosis typically attend a healthcare institution several times for evaluation of epilepsy treatment or to change non-functional shunts, it is not clear whether the presented data correspond to new cases only or if recurrent visits were also included. If the latter is true, the data would not reflect the incidence of neurocysticercosis at the INNN. In addition, no data were provided as to the precise number of parasitic cysts in these patients. Therefore, cases with few cysts were grouped with those harboring multiple parasites, with multiple cysts often causing more severe forms of the disease (3). The precise number of parasites might be important in order to understand the authors’ observation of a lower frequency of severe cases in 2004 as compared to 1994. In this regard, even the cases defined as living in Mexico City could have come from rural areas years before, as Dixon and Lipscomb (4) demonstrated that the time between infection with Taenia solium eggs and appearance of neurological symptoms can vary from a few months to 30 years. As in many parts of the world, migration to urban areas is frequent in Mexico and it has been established that close contact with a tapeworm carrier is of major importance to acquire cysticercosis (5). Since the study by Fleury et al (2) did not include the search for a tapeworm carrier in the household in order to determine the probability of a recent infection, it is not possible to state that neurocysticercosis is a persisting health problem in Mexico. Albeit we agree that this parasitic disease must be subject to surveillance, certainly the frequency of cysticercosis in Mexico has dramatically decreased (1).
References
1. Flisser A, Correa D (In press). Neurocysticercosis may no longer be a public health problem in Mexico. PLoS NTD
2. Fleury A, Moreno-Garcia J, Valdez-Aguerrebere P, de Sayve Durán M, Becerril-Rodríguez P, Larralde C, Sciutto E (2010) Neurocysticercosis, a Persisting Health Problem in Mexico. PLoS NTD, 4 Issue 8, e805
3. Fleury A, Flisser A, Flores-Rivera J, Corona T (2009) Parasitic infections. 13. Taenia solium. En: Post-Infectious Sequelae and Long-Term Consequences of Infectious Diseases. Smith JL, Brogden KA, Fratamico P (eds). American Society for Microbiology Press, p. 229-243
4. Dixon HBF, Lipscomb FM (1961) Cysticercosis: an analysis and follow up of 450 cases, Privy Council Med Res Special Rep Ser, 229: 1-58
5. Gilman RH, Del Brutto OH, Garcia HH, Martinez M, The Cysticercosis Working Group in Peru (2000) Prevalence of taeniosis among patients with neurocysticercosis is related to severity of infection. Neurology 55:1062.

Ana Flisser1*, Dolores Correa2
1. Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), Av. Universidad 3000, Col.Copilco Universidad, México 04360 DF, México. flisser@servidor.unam.mx
2. Laboratorio de Inmunología Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Av. Insurgentes Sur 3700-C, Col. Insurgentes Cuicuilco, 04530, México, DF, México. mariadol@yahoo.com
* Corresponding author

No competing interests declared.

RE: Taenia solium cysticercosis: a persisting health problem in Mexico: is it debatable?

afleury replied to flisser on 28 Nov 2010 at 04:11 GMT

In the Opening Lecture of “The First North American Parasitology Congress”, held in June of 2007 at Merida, Yucatán, México, Dr. Flisser mentioned her conviction that “T. solium has been controlled in México” (1).
Her perception did not agree with our frequent dealings with cases of human NC being attended at the Instituto Nacional de Neurología y Neurocirugía (INNN) (2), as well as with our frequent findings of porcine cysticercosis in rural areas (3). The discrepancy encouraged us to look deeper into this matter. For this purpose, two studies were done. First, a thorough reading and compilation of the 8804 hard copies of the clinical records of all patients admitted at the INNN in 1994 and 2004 was began at the end of 2007 to assess the incidence of NC (new cases) at INNN in these two years. This was done by trained medical students and residents of neurology at the INNN, supervised by an expert neurologist. We also evaluated the frequency of surgical interventions and hospitalizations at INNN on account of NC, using data from the epidemiological service of the same institution. The results of these two studies were the body of our article published by PLos NTD in August 2010.
The numerical results of our enquires commented by Flisser and Correa, are herein spelled out to make them clear for all.
- In the first part of the study a non-significant difference of 2.4 versus 2.5% of NC incidence of all the patients admitted in the INNN in the years 1994 and 2004 was reported. We considered NC cases to be “severe” if they show signs of intracranial hypertension. These patients had parasites located in the subarachnoideal basal cisterns or in the ventricular systems and constitute the most severe form of the disease (4).
- In the second part we reported a significant lower frequency of hospitalized patients in the neurosurgery service but no significant differences in the frequency of NC patients hospitalized in the neurology service of INNN in the period of 1995 and 2009. These data could reflect the more effective therapeutic protocols and/or the earliest diagnosis which result in lessening the severity of the disease. During these 15 years we cannot discard that a same patient with more than one hospitalization was accounted.

In addition, we also found a significant increase in the proportion of patients from México City between 1994 and 2004 that can be, at least in part, due to rural-urban migration as it was mentioned in our paper (Discussion, line 11).
Finally, we want to emphasize that we did not intent to identify the time of the NC infection, since we find this practically impossible in highly endemic situations albeit less so in those non endemic (5). In this respect, and in complete disagreement with Flisser and Correa's comments, the identification of a tapeworm carrier in the household of a NC patient, would not allow establishing the date of the infection, since in highly endemic situations the risk of acquiring cysticercosis is more geographically and socially extended than is a household (3). Moreover, the finding of a tapeworm carrier in the household of a NC patient does not necessarily imply there is a cause effect relationship between them, since both infections are chronic diseases and could have been acquired at different times and places. It must be also noted, that in our study the age of new patients was similar in 1994 and in 2004, a finding that argues against the notion that infections are only old ones.

The main message of our article is to show the persistence and NC´s morbidity nowadays in México by using reliable and verifiable numerical data instead of “official date”. In consequence, effective actions in preventing Taenia solium transmission in endemic countries are to be much encouraged instead of neglected.

Agnès Fleury1,2, Carlos Larralde2, Edda Sciutto2.

1. Instituto Nacional de Neurología y Neurocirugía, México City, México.
2. Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México City.

References
1- Flisser A, Narro J, Calderon J, Martínez G (2007) A national Model for the control of a parasitic disease: Human cysticercosis in México. Abstract, From Alaska to Chiapas: The first North American Parasitology Congress, Merida, México, pp 55.
2- Fleury A, Dessein A, Dumas M, Preux PM, Tapia G, et al. (2004) Symptomatic neurocysticercosis: host and exposure factors relating with disease heterogeneity. Journal of Neurology 251: 830-837.
3- Morales J, Martínez JJ, Rosetti M, Fleury A, Maza V, et al. (2008) Spatial distribution of Taenia solium porcine cysticercosis within a rural area of Mexico. PLoS Negl Trop Dis 2: e284.
4- Fleury A, Carrillo-Mezo R, Flisser A, Sciutto E, Corona T. Subarachnoid basal neurocysticercosis: a focus on the most severe form of the disease. Expert Review of Anti-infective Therapy (In press).
5- Schantz PM, Moore AC, Muñoz JL, Hartman BJ, Schaefer JA, et al. (1992) Neurocysticercosis in an Orthodox Jewish community in New York City. N Engl J Med. 327: 692-695.

No competing interests declared.

RE: RE: Taenia solium cysticercosis: a persisting health problem in Mexico: is it debatable?

malcolmJ replied to afleury on 12 Jan 2011 at 00:51 GMT

The article by Ana Flisser and Dolores Correa can be found at: http://www.plosntds.org/a...

No competing interests declared.