Recrudescence

Recrudescence is the recurrence of an undesirable condition. In medicine, it is usually defined as the recurrence of symptoms after a period of remission or quiescence,^[1]^[2]^[3] in which sense it can sometimes be synonymous with relapse. In a narrower sense, it can also be such a recurrence with higher severity than before the remission.^[3] "Relapse" conventionally has a specific (albeit somewhat illogical) meaning when used in relation to malaria (see below).

Malaria

In malaria, recurrence can take place due to recrudescence; or relapse; or re-infection (via mosquito transmission). Relapse means that a recurrence has been precipitated by a dormant stage in the liver called a "hypnozoite".^[4] Thus, relapse is applied only for those plasmodial species that have hypnozoites in the life cycle, such as Plasmodium vivax and P. ovale. On the other hand, recrudescence means that circulating, multiplying parasites are detected after having persisted in the bloodstream (or elsewhere) at undetectable levels for a period of time, as merozoites (as opposed to hypnozoites).^[5] This term is applied for Plasmodium species that are not associated with hypnozoite-mediated recurrences, such as P. falciparum, P. malariae, and P. knowlesi. Recrudescence is also used for malarial recurrence caused by drug-resistant strains of P. vivax and P. ovale where parasites remained in the bloodstream despite treatment.^[6]^[7]

Melioidosis

In melioidosis, a recurrent infection can be due to re-infection and relapse. Re-infection is a recurrence of symptoms due to an infection with a new strain of Burkholderia pseudomallei following the eradication therapy of melioidosis. Meanwhile, relapse are those who presented with melioidosis symptoms due to failure to clear the infection in the bloodstream after completion of eradication therapy. On the other hand, recrudescence is the recurrence of melioidosis symptoms during the eradication therapy.^[8]^[9]

Bovine viral diarrhoea

The bovine viral diarrhoea virus (bovine virus diarrhea) is said to be recrudescent for some time after clinical signs have abated, because antibodies plateau c. weeks 10–12, and are not lifelong, auto infection may potentially occur in the acutely infected non-pregnant animal.

Others

Other diseases that may recur following a short or long period of quiescence include shingles (after chicken pox), oral herpes and genital herpes, and Brill–Zinsser disease (after epidemic typhus).

References

^ Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
^ Wolters Kluwer, Stedman's Medical Dictionary, Wolters Kluwer.
^ ^a ^b Merriam-Webster, Merriam-Webster's Medical Dictionary, Merriam-Webster.
^ Markus, MB (2011). "Malaria: Origin of the term "hypnozoite"". Journal of the History of Biology. 44 (4): 781–786. doi:10.1007/s10739-010-9239-3. PMID 20665090.
^ Markus, MB (2022). "Theoretical origin of genetically homologous Plasmodium vivax malarial recurrences". Southern African Journal of Infectious Diseases. 37 (1): 369. doi:10.4102/sajid.v37i1.369. PMC 8991251. PMID 35399558.
^ "The Department of Health - Australia - Malaria Laboratory Case Definition (LCD)". Australian Department of Health. Archived from the original on 29 July 2020. Retrieved 21 December 2020. "Recrudescence" is the term for recurrence of infection with all malaria species including P. falciparum, P. malariae and P. knowlesi, which lack hypnozoites. This occurs when the infection (unless a new infection) has persisted in the blood at undetectable levels and then becomes detectable again. ... . If, following reactivation of a latent hypnozoite in the liver, a relapse occurred, then that individual would, potentially, be able to spread the infection to mosquitoes (provided that there were gametocytes in the blood). Malaria epidemiologists consider that each relapse has the potential to establish a new focus of transmission and, thus constitutes a new case. ... In the case of the persistence of drug-resistant parasites, there would be no clearance of parasitaemia even though it might be reduced to sub-patent levels for a time. This would be the same case but, in this instance, recurrence would be termed "recrudescence" not "relapse" (refer above). The period of 8 weeks used to exclude recrudescence as the cause of recurrences of chloroquine-resistant P. vivax is somewhat arbitrary, but it does extend beyond the period during which there would be sufficient drug present to suppress the resistant parasites below patency.
^ Markus MB (July 2017). "Malaria Eradication and the Hidden Parasite Reservoir". Trends in Parasitology. 33 (7): 492–495. doi:10.1016/j.pt.2017.03.002. PMID 28366603.
^ Sarovich DS, Ward L, Price EP, Mayo M, Pitman MC, Baird RW, Currie BJ (February 2014). "Recurrent melioidosis in the Darwin Prospective Melioidosis Study: improving therapies mean that relapse cases are now rare". Journal of Clinical Microbiology. 52 (2): 650–3. doi:10.1128/JCM.02239-13. PMC 3911345. PMID 24478504. Recurrent melioidosis can result either from relapse due to failure to clear an infection or from reinfection with a new B. pseudomallei strain. ... Patients re-presenting during this period of therapy are considered to have recrudescent rather than recurrent melioidosis and have been excluded from our analysis.
^ Pitman MC, Luck T, Marshall CS, Anstey NM, Ward L, Currie BJ (March 2015). Vinetz JM (ed.). "Intravenous therapy duration and outcomes in melioidosis: a new treatment paradigm". PLOS Neglected Tropical Diseases. 9 (3): e0003586. doi:10.1371/journal.pntd.0003586. PMC 4374799. PMID 25811783. This approach is associated with rates of relapse, defined as recurrence following the eradication phase, that can exceed 5%. Rates of recrudescence, defined as recurrence during the eradication phase, have not previously been reported.

[Dorlands-1] Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.

[Stedmans-2] Wolters Kluwer, Stedman's Medical Dictionary, Wolters Kluwer.

[MW_Medical-3] Merriam-Webster, Merriam-Webster's Medical Dictionary, Merriam-Webster.

[4] Markus, MB (2011). "Malaria: Origin of the term "hypnozoite"". Journal of the History of Biology. 44 (4): 781–786. doi:10.1007/s10739-010-9239-3. PMID 20665090.

[5] Markus, MB (2022). "Theoretical origin of genetically homologous Plasmodium vivax malarial recurrences". Southern African Journal of Infectious Diseases. 37 (1): 369. doi:10.4102/sajid.v37i1.369. PMC 8991251. PMID 35399558.

[6] "The Department of Health - Australia - Malaria Laboratory Case Definition (LCD)". Australian Department of Health. Archived from the original on 29 July 2020. Retrieved 21 December 2020. "Recrudescence" is the term for recurrence of infection with all malaria species including P. falciparum, P. malariae and P. knowlesi, which lack hypnozoites. This occurs when the infection (unless a new infection) has persisted in the blood at undetectable levels and then becomes detectable again. ... . If, following reactivation of a latent hypnozoite in the liver, a relapse occurred, then that individual would, potentially, be able to spread the infection to mosquitoes (provided that there were gametocytes in the blood). Malaria epidemiologists consider that each relapse has the potential to establish a new focus of transmission and, thus constitutes a new case. ... In the case of the persistence of drug-resistant parasites, there would be no clearance of parasitaemia even though it might be reduced to sub-patent levels for a time. This would be the same case but, in this instance, recurrence would be termed "recrudescence" not "relapse" (refer above). The period of 8 weeks used to exclude recrudescence as the cause of recurrences of chloroquine-resistant P. vivax is somewhat arbitrary, but it does extend beyond the period during which there would be sufficient drug present to suppress the resistant parasites below patency.

[7] Markus MB (July 2017). "Malaria Eradication and the Hidden Parasite Reservoir". Trends in Parasitology. 33 (7): 492–495. doi:10.1016/j.pt.2017.03.002. PMID 28366603.

[8] Sarovich DS, Ward L, Price EP, Mayo M, Pitman MC, Baird RW, Currie BJ (February 2014). "Recurrent melioidosis in the Darwin Prospective Melioidosis Study: improving therapies mean that relapse cases are now rare". Journal of Clinical Microbiology. 52 (2): 650–3. doi:10.1128/JCM.02239-13. PMC 3911345. PMID 24478504. Recurrent melioidosis can result either from relapse due to failure to clear an infection or from reinfection with a new B. pseudomallei strain. ... Patients re-presenting during this period of therapy are considered to have recrudescent rather than recurrent melioidosis and have been excluded from our analysis.

[9] Pitman MC, Luck T, Marshall CS, Anstey NM, Ward L, Currie BJ (March 2015). Vinetz JM (ed.). "Intravenous therapy duration and outcomes in melioidosis: a new treatment paradigm". PLOS Neglected Tropical Diseases. 9 (3): e0003586. doi:10.1371/journal.pntd.0003586. PMC 4374799. PMID 25811783. This approach is associated with rates of relapse, defined as recurrence following the eradication phase, that can exceed 5%. Rates of recrudescence, defined as recurrence during the eradication phase, have not previously been reported.

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