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Letter to the editor regarding - pleural effusion caused by Trichinella spiralis infection: two case reports

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We read with interest the paper entitled “Pleural effusion caused by Trichinella spiralis infection: two case reports”, published by Pan and colleagues in a recent issue of your journal [1]. In brief, the authors described two cases of exudative pleurisy with a high level of mononuclear cells and a positive Trichinella serology. As a matter of fact, pleurisy is not a frequent occurrence during trichinellosis. According to Pawlowski [2], pleurisy can be observed during trichinellosis, either associated with migrating focal lung infiltrations (exudate), or because of hypoalbuminemia and/or circulatory complications (transudate). Gould [3] reports that “pleuritis is infrequent, generally dry, occurs mainly during the later weeks of infection, and is of short duration. A serous effusion may be a manifestation of congestive heart failure”. In the present case, the authors stated that due to a positive Trichinella serology and in the absence of other identified causes, these pleural effusions could be of parasite origin. However, the presence of Trichinella antibodies does not necessarily indicate an active infection, as the antibodies can persist in the blood for months or even years after the initial infection has been overcome [4]. Moreover, no clinical signs of acute trichinellosis (fever, myalgia, or facial edema) were reported. Rather, case 1 acquired trichinellosis from eating undercooked pork sausages 1.5 months before the occurrence of pleuritis and then showed gastrointestinal symptoms (diarrhea). These observations are not definitive proof of Trichinella infection. In addition, the patient had no muscular involvement, and it is well known that muscular pain usually lasts for several weeks after an infection with Trichinella. Pleural fluid cytology analysis of the two cases detected the presence of lymphocytes (not eosinophils), suggesting tuberculosis or malignancies, as mentioned by the authors. Nevertheless, case 1 displayed no obvious abnormality by either sonography (urological and cardiac), or positron emission tomography. Other possible causes of pleurisy were not investigated, such as viral infections or sarcoidosis, as well as connective tissue disorders [5, 6].

As mentioned by the authors, “the detection of parasite antibody IgG indicated Trichinella spiralis (+) by ELISA”. No information is provided about the method used (commercial or home-made test?), or the level of sensitivity and specificity. ELISA is a quantitative method for calculating antibody amounts. The sign + suggests only the presence of antibodies, but not the titer that if low might be compatible with an ancient infection. Several authors have reported on persistence of antibodies, explained by the long survival of Trichinella encapsulated larvae in muscles. Harms et al. [7] in a prospective controlled study of patients found that 38% of the 128 originally infected patients still had IgG antibodies to Trichinella ten years after acute infection. Kociecka et al. [8] identified antibodies in patients infected seven years before. In a study re-evaluating subjects 15 years after they were involved in a trichinellosis outbreak, Pinelli et al. [9] showed by different techniques (ELISA, western-blot) that antibodies were present in nearly all patients. Illic et al. [10] reported anti-Trichinella antibodies in 10 out of 12 patients who acquired trichinellosis between 13 and 18 years before. Therefore, the serological results must be evaluated in conjunction with the individual’s medical history, clinical symptoms, and other laboratory tests to establish a definitive diagnosis. Furthermore, it’s important to note that there are other conditions and infections that can cause a positive Trichinella antibody test, such as other parasitic infections, autoimmune disorders, or cross-reactivity with other antigens. These false-positive results can be eliminated by using more specific techniques, such as western-blot [11].

In the Discussion there are also probable typing or translation mistakes. When describing circulating antigens, the authors stated that these antigens were “produced by live insects”. And further, “after being treated with insect repellent (albendazole or mebendazole), pleural effusion was absorbed, so it was diagnosed as trichinosis”. Trichinella is not an insect, and albendazole and mebendazole are anthelminthic drugs and not insect repellents. The authors should also use throughout the text the word trichinellosis, instead of trichinosis, to designate the disease caused by Trichinella.

To resume, it’s difficult to confirm a link between pleurisy and Trichinella, since the search for alternative causes was not exhaustive combined with a lack of suggestive standard clinical and biological data consistent with active and/or recent trichinellosis. The favorable evolution could have been spontaneous if the pleural effusion had been caused by viruses. Albendazole and mebendazole could have enhanced this favorable evolution through their anti-inflammatory effects, as suggested by recent experimental studies in rodents [12, 13].

This letter is dedicated to Fabien Vaylet who passed away after the initial submission of the manuscript. We also thank Gordon Langsley for the final language revision.

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  1. Pan ZZ, Zhu MJ, Rong YQ, Yang J. Pleural effusion caused by Trichinella spiralis infection: two case reports. BMC Infect Dis. 2023;23:77.

    Article  PubMed  PubMed Central  Google Scholar 

  2. Pawlowski ZS. Clinical aspects in man. In: Campbell WC, editor. Trichinella and trichinosis. New York and London: Plenum; 1983. pp. 367–401.

    Chapter  Google Scholar 

  3. Gould SE. Clinical manifestations. In: Gould SE, editor. Trichinosis in man and animals. Springfield: Charles Thomas; 1970. pp. 269–306.

    Google Scholar 

  4. Bruschi F, Dupouy-Camet J, Trichinellosis. In: Bruschi F, editor. Helminth infections and their impact on Global Public Health. 2nd ed. Vienna: Springer; 2022. pp. 351–96.

    Chapter  Google Scholar 

  5. Sahn SA. Getting the most from pleural fluid analysis. Respirology. 2012;17:270.

    Article  ADS  PubMed  Google Scholar 

  6. Nestor J, Huggins T, Kummerfeldt C, DiVietro M, Walters K, Sahn S. Viral diseases affecting the pleura. J Clin Virol. 2013;58:367.

    Article  PubMed  Google Scholar 

  7. Harms G, Binz P, Feldmeier H, Zwingenberger K, Schleehauf D, Dewes W, et al. Trichinosis: a prospective controlled study of patients ten years after acute infection. Clin Infect Dis. 1993;17:637.

    Article  CAS  PubMed  Google Scholar 

  8. Kociecka W, Bruschi F, Marini C, Mrozewicz B, Pielok L. Clinical appraisal of patients and detection of serum antibodies by ELISA and CIA tests in late periods of Trichinella sp. invasion. Parasite. 2001;8(2 Suppl):147.

    Article  Google Scholar 

  9. Pinelli E, Mommers M, Kortbeek LM, Castagna B, Piergili-Fioretti D, Bruschi F. Specific IgG4 response directed against the 45-kDa glycoprotein in trichinellosis: a re-evaluation of patients 15 years after infection. Eur J Clin Microbiol Infect Dis. 2007;26:641.

    Article  CAS  PubMed  Google Scholar 

  10. Ilic N, Vasilev S, Gruden-Movsesijan A, Gnjatovic M, Sofronic-Milosavljevic L, Mitic I. Long lasting immunity in trichinellosis - insight from a small study group. J Helminthol. 2022;96:e35.

    Article  CAS  PubMed  Google Scholar 

  11. Yera H, Andiva S, Perret C, Limonne D, Boireau P, Dupouy-Camet J. Development and evaluation of a Western blot kit for diagnosis of human trichinellosis. Clin Diagn Lab Immunol. 2003;10:793.

    PubMed  PubMed Central  Google Scholar 

  12. Wildenberg ME, Levin AD, Ceroni A, Guo Z, Koelink PJ, Hakvoort TBM, et al. Benzimidazoles Promote Anti-TNF Mediated Induction of Regulatory Macrophages and enhance therapeutic efficacy in a murine model. J Crohns Colitis. 2017;11:1480.

    Article  PubMed  PubMed Central  Google Scholar 

  13. Badripour A, Behzadi M, Hassanipour A, Azar PRS, Rahbar A, Abbaslou Z, et al. Albendazole ameliorates inflammatory response in a rat model of acute mesenteric ischemia reperfusion injury. Biomed Pharmacother. 2022.

    Article  PubMed  Google Scholar 

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This letter is dedicated to Fabien Vaylet who passed away after the initial submission of the manuscript. We also thank Gordon Langsley for the final language revision.


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JDC wrote the paper. FV analyzed and interpreted the data regarding the pleural effusion. JDC & FB analysed the parasitological and immunological data. All authors read and approved the final manuscript.

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Correspondence to Jean Dupouy-Camet.

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Editor’s note: The Editors have invited a response from the authors of the published article to which this Matters Arising refers. At the time of publication, the authors had not submitted their response.

Fabien Vaylet: deceased.

JDC and FB are members of the International Commission on Trichinellosis submitted.

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Dupouy-Camet, J., Vaylet, F. & Bruschi, F. Letter to the editor regarding - pleural effusion caused by Trichinella spiralis infection: two case reports. BMC Infect Dis 24, 291 (2024).

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