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Evolutionary Biology of Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
However, other experimental results suggest a more nuanced and opposite effect. Consider Plasmodium chabaudi, a mosquito-transmitted parasite of mice. Serial syringe passage results in parasites with high levels of virulence that cause high levels of parasitemia in red blood cells (Figure 7.17A). The faster growing forms would come to predominate and be favored by artificial syringe transfer of infected blood to uninfected mice. This idea has been called the short-sighted hypothesis. The predominance of more rapidly reproducing (virulent) strains might be expected to translate into their greater transmission success to mosquitoes, if mosquitoes happen to be present. Otherwise, the virulent parasites might simply cause the early death of their host, hence the notion that such an approach is “short-sighted.” However, when P. chabaudi was allowed to infect its Anopheles mosquito vector and mouse infections were initiated by bites of infected mosquitoes, a significantly reduced level of parasitemia and virulence in mice was noted (Figure 7.17A). Passage through the vector had the effect of modifying expression of members of the pir gene family in asexual blood stage parasites in the mice. This in turn altered the mouse immune response and lead to attenuation of parasite growth and pathology.
Toxoplasmosis
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
The latent or chronic stage is manifested by tissue cysts in most organs. The brain, skeletal muscle, cardiac muscle, and placenta are the most common sites for tissue cysts, which may be identified by periodic acid-Schiff stain. Recurrent parasitemia is rare in immunocompetent individuals. However, under immunodepressed states, especially AIDS, the cysts may reactivate and cause parasitemia and tissue destruction.
Neuroinfectious Diseases
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Jeremy D. Young, Jesica A. Herrick, Scott Borgetti
The definitive hosts for G. spinigerum are dogs and cats, from which eggs are passed in the feces.2 Larvae are ingested by crustaceans, which are eaten by other animal hosts. When humans ingest the muscle tissue of these hosts, parasitemia can lead to cutaneous, visceral, or CNS infection. Clinical symptoms occur with migration of the parasite within host tissues. Gnathostoma is not as neurotropic and can manifest in many tissues. It has been suggested that one factor that may contribute to the increasing geographic range of this organism could be the increasing availability of imported seafood that in many cases is consumed raw.6
Evaluating the dual reactivity on SD bioline malaria rapid diagnosis tests as a potential indicator of high parasitemia due to Plasmodium falciparum
Published in Pathogens and Global Health, 2021
Roman Rodrigue Dongang Nana, Valerie Makoge, Ngum Lesley Ngum, Nathalie Amvongo-Adjia, Vineeta Singh, Roger Moyou Somo
In both study sites, 483 samples were obtained where 314 (65.0%) samples were from Efoulan and 169 (34.9%) from Mfou district hospitals. The mean age was 28.9 ± 1.0 years in the study population with mostly female patients representing at least 55.9% (270/483) of the participants (Table 1). Stratifying the age distribution further in the patients found positive by all three diagnostic tests would have reduced the number of patients per stratum for analysis hence, it was not done in the reported study. Malaria RDTs showed reactivity in 33.3% (161/483) of the cases, for HRP2 alone and HRP2/pLDH together were found in 63.4% (102/161) and 36.6% (59/161) of the cases respectively. The prevalence of malaria by microscopy and PCR assay were 18.0% (87/483) and 31.7% (153/483) respectively (Figure 2). Parasitemia in the study population ranged from 40 to 226,000 parasites/µl of blood for a geometric mean 3052 (95% CI: 1771–5260) parasites/µl of blood.
Oxidative stress implications for therapeutic vaccine development against Chagas disease
Published in Expert Review of Vaccines, 2021
Subhadip Choudhuri, Lizette Rios, Juan Carlos Vázquez-Chagoyán, Nisha Jain Garg
Clinically, upon exposure to the parasite, flu-like symptoms associated with acute blood parasitemia are commonly noted. Parasites become practically undetectable in the blood in 2–4 months after infection, though infected individuals remain seropositive for T. cruzi-specific antibodies. Decades after initial parasite exposure, ~30% of the infected individuals eventually advance to the clinical phase of chronic CD that is presented with cardiac hypertrophy progressing to dilated cardiomyopathy and heart failure. Clinical evidence of digestive or neurological disorders may also be presented in Chagas patients (reviewed in [7]). Currently, CD is estimated to affect 6–8 million people that result in 10–12,000 deaths per year [8]. Approximately, 71 million people are exposed to risk of infection and ~28,000 new cases of T. cruzi infection occur every year [9,10].
Management strategies for human babesiosis
Published in Expert Review of Anti-infective Therapy, 2020
Robert P. Smith, Klaus-Peter Hunfeld, Peter J Krause
Mild to moderate babesiosis is typical in those with mild immune suppression but who are otherwise in good health, such as those with well-controlled non-AIDS HIV or those on steroid treatment for another underlying condition [76]. Some of these patients can be managed as outpatients in a similar manner as immunocompetent patients but most will initiate treatment in a hospital setting. The combination of atovaquone and azithromycin given for 7 to 10 days is usually effective (Table 1). If gastrointestinal symptoms preclude oral administration, azithromycin may be given intravenously. The alternative regimen of clindamycin (intravenous or oral) and quinine (oral) can be used if needed but is more likely to cause side effects. Resolution of systemic inflammatory symptoms such as fever is expected during the first week of treatment. Hemolytic anemia, if present, stabilizes. Symptoms such as fatigue may persist for weeks despite resolution of parasitemia. Close monitoring during acute disease and follow up is advised for this group of patients until infection has cleared. Patients should be instructed to report any new symptoms suggestive of babesiosis to their physician, in which case a thin blood smear and PCR should be performed.