X disease epidemic in Congo: X agents are not new to Science!
Despite the occurrence of a coinfection by Plasmodium falciparum, P. vivax and/or P. malariae - the causative agents of malaria, that is endemic in Africa - in 80% of these frequently undernourished patients, which gets along very with the anemia commonly experienced by them, the disease aetiology is still unknown. Within such context, the diagnostic suspicions made publicly available by the World Health Organization (WHO) include measles, influenza, acute pneumonia, COVID-19, haemolytic uremic syndrome and malaria (https://www.who.int/
Alongside anemia, additional symptoms frequently seen in affected individuals include sneezing, cough, dyspnea, headache, fatigue and fever, with these clinical signs supporting a primary aetiologic role played by one or more viral or non-viral, human or zoonotic, respiratory pathogens.
Mutatis mutandis, well before the Human Immunodeficiency Virus (HIV), the AIDS agent, was simultaneously identified in 1983 by Luc Montagnier (in France) and by Robert Gallo (in USA), a fungal agent formerly termed Pneumocystis carinii and then renamed P. jirovecii had been deemed responsible, being subsequently (more than two years later!) regarded as one of the many opportunistic pathogens causing secondary infections in AIDS-affected and, in general, in immunocompromised patients (1). As a matter of fact, fungal and protozoan agents are frequently responsible for opportunistic infections in humans as well as in animals primarily affected by both viral and non-viral immunodeficiencies. This is the case, for instance, of Canine Distemper Virus (CDV)-infected dogs and of Cetacean Morbillivirus (CeMV)-infected dolphins and whales, in which a Toxoplasma gondii coinfection may be commonly found, similarly to HIV-infected people (2).
Since P. falciparum, P. vivax, and P. malariae are themselves protozoan pathogens, an opportunistic role played by such agents in the etiology of the "new" disease reported among DRC patients should not be ruled out.
Furthermore, when delving into the charming "history of (human and animal) infectious diseases", before the discovery of the SARS-CoV betacoronavirus in 2002 on behalf of Carlo Urbani - the Italian physician who then succumbed to SARS -, Chlamydia spp., a bacterial pathogen, was deemed to be the cause of SARS (3). Likewise, before Phocine Distemper Virus (PDV, another Morbillivirus genus member) was recognized as the primary cause of the mass mortality outbreaks affecting North Sea common seal (Phoca vitulina) and gray seal (Halichoerus grypus) populations in 1988 (4), a Herpesvirus was deemed to be responsible for these dramatic die-offs (5).
Invertebrate organisms do not seem to represent an "exception to the rule", provided that the etiology of the mass mortality events involving in recent years noble pen shells (Pinna nobilis) in the Mediterranean Sea region had been attributed to both protozoan (Haplosporidium pinnae) and bacterial pathogens (Mycobacterium sherrisii, Vibrio mediterranei) before the primary causative agent (a small RNA virus belonging to Picornavirales) was identified (6).
In conclusion, the discovery of the primary cause(s) of any new infectious (and non-infectious) disease condition appears to be unavoidably preceded by "errors" made by the Scientific Community before the "true" etiology will be found, with this challenging process being made much easier and much more fascinating by a multidisciplinary research effort constantly inspired by the "One Health" principle.
Historia Magistra Vitae!
REFERENCES
1) Wickramasekaran RN, Jewell MP, Sorvillo F, Kuo T. The changing trends and profile of pneumocystosis mortality in the United States, 1999-2014. Mycoses 2017; 60: 607-15.
2) Di Guardo G, Proietto U, Di Francesco CE, et al. Cerebral toxoplasmosis in striped dolphins (Stenella coeruleoalba) stranded along the Ligurian Sea coast of Italy. Vet Pathol 2010; 47: 245-53.
3) World Health Organization (WHO). SARS: How a global epidemic was stopped. WHO Western Pacific Region, 2006, pp. 1-318 (ISBN 9290612134).
DOI: https://apps.who.int/iris/
4) Duignan PJ, Van Bressem MF, Baker JD, et al. Phocine distemper virus: Current knowledge and future directions. Viruses 2014; 6: 5093-134.
5) Osterhaus AD. Seal death. Nature 1988; 334: 301-2.
6) Carella F, Prado P, De Vico G, et al. A widespread picornavirus affects the hemocytes of the noble pen shell (Pinna nobilis), leading to its immunosuppression. Front Vet Sci 2023; 10: 1273521.
Please sign in or register for FREE
If you are a registered user on Research Communities by Springer Nature, please sign in