Acquired toxoplasmosis; observations on two parasitologically proved cases treated with pyrimethamine and triple sulfonamides

Novel therapeutic opportunities for Toxoplasma gondii, Trichomonas vaginalis and Giardia intestinalis infections

INTRODUCTION

Toxoplasma gondii, Trichomonas vaginalis and Giardia intestinalis are the causative agents of Toxoplasmosis, Trichomoniasis and Giardiasis, three important infections threatening human health and affecting millions of people worldwide. Although drugs and treatment are available to fight these protozoan parasites, side-effects and increasing drug resistance, require continuous efforts for the development of novel effective drugs.

AREAS COVERED

The patents search was carried out in September/October 2022 with four official scientific databases (Espacenet, Scifinder, Reaxys, Google Patents). Treatments for Toxoplasmosis, Trichomoniasis and Giardiasis (2015-2022) have been grouped according to their chemotypes. In particular, novel chemical entities have been reported and investigated for their structure-activity relationship, when accessible. On the other hand, drug repurposing, extensively exploited to obtain novel anti-protozoal treatment, has been in-depth described. Finally, natural metabolites and extracts have also been reported.

EXPERT OPINION

T. gondii, T. vaginalis and G. intestinalis are protozoan infections usually controlled by immune system in immunocompetent patients; however, they could represent a threatening health for immunocompromised people. The needs of novel effective drugs, endowed with new mechanisms of actions arises from the increasing drug resistance affecting antibiotic as well as antiprotozoal therapies. In this review different therapeutic approaches to treat protozoan infections have been reported.

Study of toxoplasmosis and toxocariasis in patients suffering from ophthalmic disorders using serological and molecular methods

Introduction

Toxoplasma gondii is an intracellular protozoan parasite that can cause ocular toxoplasmosis with most complications such as retinal detachment. Toxocara parasite, round worm, found in dogs and cats appears as larva migrans in humans can cause serious ocular complications such as debilitating vision loss.In Khuzestan province, southwest of Iran, T. gondii infection has been reported to be significant but toxocariasis was rare. However, the frequency of ocular toxoplasmosis and toxocariasis has not been studied in this area. The aim of this study was to evaluate the ocular toxoplasmosis and ocular toxocariasis using serological and molecular methods.

Method

In this case control study, 310 patients were identified by ophthalmologist as ocular toxoplasmosis and then 5 cc of venous blood samples were taken from each of them. Serum samples and buffy coat were prepared and ELISA was used to detect IgG and IgM anti-Toxoplasma antibodies and the molecular PCR was used to detect Toxoplasma DNA parasite in buffy coats. ELISA test was used to detect of IgG anti-Toxocara antibodies.

Results

Totally, for ocular toxoplasmosis, 130 (41.93%) of 310 patients were positive by ELISA, of them 121 (39%) IgG positive and nine (2.9%) IgM positive were diagnosed. Of 121 cases with IgG⁺, 119 (98.35%) were diagnosed with high IgG avidity indicating chronic phase of the infection. For ocular toxocariasis evaluation, antibodies against Toxocara were not detected in any of the samples. By PCR molecular method, 11 out of 310 patients (3.54%) had T. gondii DNA in the blood. In control, in total, 21 cases were detected positive by serology method, which showed a significant difference with the results of the case group(P < 0.05).By PCR method, only three cases showed positive which also indicated significant difference with result of case group (3 vs 9) (P < 0.05). In the control group, also no anti-toxocara antibodies were found.

Conclusion

It can be concluded that T. gondii in Khuzestan province as the etiologic agent of ocular toxoplasmosis and physicians should consider diagnostic methods for identifying the infection when they visit the patients.

Treatment of Toxoplasmosis: Historical Perspective, Animal Models, and Current Clinical Practice

Primary Toxoplasma gondii infection is usually subclinical, but cervical lymphadenopathy or ocular disease can be present in some patients. Active infection is characterized by tachyzoites, while tissue cysts characterize latent disease. Infection in the fetus and in immunocompromised patients can cause devastating disease. The combination of pyrimethamine and sulfadiazine (pyr-sulf), targeting the active stage of the infection, is the current gold standard for treating toxoplasmosis, but failure rates remain significant. Although other regimens are available, including pyrimethamine in combination with clindamycin, atovaquone, clarithromycin, or azithromycin or monotherapy with trimethoprim-sulfamethoxazole (TMP-SMX) or atovaquone, none have been found to be superior to pyr-sulf, and no regimen is active against the latent stage of the infection. Furthermore, the efficacy of these regimens against ocular disease remains uncertain. In multiple studies, systematic screening for Toxoplasma infection during gestation, followed by treatment with spiramycin for acute maternal infections and with pyr-sulf for those with established fetal infection, has been shown to be effective at preventing vertical transmission and minimizing the severity of congenital toxoplasmosis (CT). Despite significant progress in treating human disease, there is a strong impetus to develop novel therapeutics for both the acute and latent forms of the infection. Here we present an overview of toxoplasmosis treatment in humans and in animal models. Additional research is needed to identify novel drugs by use of innovative high-throughput screening technologies and to improve experimental models to reflect human disease. Such advances will pave the way for lead candidates to be tested in thoroughly designed clinical trials in defined patient populations.

The histological diagnosis of toxoplasmic lymphadenitis

The commonest presenting sign of acquired toxoplasmosis in man is enlargement of superficial lymph nodes. The persistence of the nodes may lead to a suspicion of malignant lymphoma and the diagnosis then hinges on the lymph node biopsy. Three cases of toxoplasmic lymphadenitis are described in each of which the diagnosis was unsuspected clinically. The chance discovery of a toxoplasma cyst in the lymph node section of Case 1 led to the correct diagnosis, after an initial diagnosis of Hodgkin's disease had been made. In the other two, strikingly similar histological changes in the lymph node biopsies suggested the diagnosis, which was confirmed serologically in each case. The histological changes are described and the clinical and pathological aspects of toxoplasmic lymphadenitis are briefly reviewed, with special reference to the differentiation from malignant lymphomatous conditions and to the specificity of the histological picture. It is concluded that the histology is, in many instances, sufficiently distinctive for a tentative diagnosis of toxoplasmic lymphadenitis to be made on the lymph node biopsy. The diagnosis should always be confirmed by isolation of the parasite or by serological tests. It is exceedingly rare for toxoplasma cysts to be found in lymph nodes and only one previous observation of this kind has been reported.

Toxoplasmosis

Toxoplasma gondii is a protozoan parasite that infects up to a third of the world's population. Infection is mainly acquired by ingestion of food or water that is contaminated with oocysts shed by cats or by eating undercooked or raw meat containing tissue cysts. Primary infection is usually subclinical but in some patients cervical lymphadenopathy or ocular disease can be present. Infection acquired during pregnancy may cause severe damage to the fetus. In immunocompromised patients, reactivation of latent disease can cause life-threatening encephalitis. Diagnosis of toxoplasmosis can be established by direct detection of the parasite or by serological techniques. The most commonly used therapeutic regimen, and probably the most effective, is the combination of pyrimethamine with sulfadiazine and folinic acid. This Seminar provides an overview and update on management of patients with acute infection, pregnant women who acquire infection during gestation, fetuses or infants who are congenitally infected, those with ocular disease, and immunocompromised individuals. Controversy about the effectiveness of primary and secondary prevention in pregnant women is discussed. Important topics of current and future research are presented.

Rheumatic manifestations of parasitic diseases

OBJECTIVES

To consolidate the spectrum and frequency of parasite-related rheumatic syndromes, which have largely been regarded as exceedingly rare by the general medicine, infectious disease, and rheumatology literature.

METHODS

A MEDLINE search was performed for articles on rheumatic syndromes related to parasitic infections published from 1966 through December 2000. Identified articles included clinical and epidemiologic studies describing cases of rheumatic syndromes associated with verified parasitic infection.

RESULTS

Rheumatologic syndromes, including inflammatory arthritis, inflammatory myositis, and vasculitis, have been described among multiple different parasite infections of all parasitic divisions, including Protozoa, Nematoda, and Platyhelminthes. Individual parasitic divisions are often associated with particular rheumatic syndromes, such as reactive arthritis and spondyloarthropathy, inflammatory or infectious myositis, and reactive or parainfectious vasculitis.

CONCLUSIONS AND RELEVANCE

Parasitic infection may underlie the clinical presentation of some rheumatic conditions. Given the continued and growing number of patients at risk for parasitosis by virtue of their country of origin, travel habits, and an immunocompromised state, potential parasitosis must be considered in patients undergoing evaluation for rheumatic complaints.

Laboratory-acquired parasitic infections from accidental exposures

Parasitic diseases are receiving increasing attention in developed countries in part because of their importance in travelers, immigrants, and immunocompromised persons. The main purpose of this review is to educate laboratorians, the primary readership, and health care workers, the secondary readership, about the potential hazards of handling specimens that contain viable parasites and about the diseases that can result. This is accomplished partly through discussion of the occupationally acquired cases of parasitic infections that have been reported, focusing for each case on the type of accident that resulted in infection, the length of the incubation period, the clinical manifestations that developed, and the means by which infection was detected. The article focuses on the cases of infection with the protozoa that cause leishmaniasis, malaria, toxoplasmosis, Chagas' disease (American trypanosomiasis), and African trypanosomiasis. Data about 164 such cases are discussed, as are data about cases caused by intestinal protozoa and by helminths. Of the 105 case-patients infected with blood and tissue protozoa who either recalled an accident or for whom the likely route of transmission could be presumed, 47 (44.8%) had percutaneous exposure via a contaminated needle or other sharp object. Some accidents were directly linked to poor laboratory practices (e.g., recapping a needle or working barehanded). To decrease the likelihood of accidental exposures, persons who could be exposed to pathogenic parasites must be thoroughly instructed in safety precautions before they begin to work and through ongoing training programs. Protocols should be provided for handling specimens that could contain viable organisms, using protective clothing and equipment, dealing with spills of infectious organisms, and responding to accidents. Special care should be exercised when using needles and other sharp objects.

Toxoplasma gondii stimulates the release of 13- and 9-hydroxyoctadecadienoic acids by human platelets

We have recently demonstrated a novel cytotoxic effect of human platelets against Toxoplasma gondii and a role for thromboxane (TX) in this process (Yong et al., 1991). We now report on the spectrum of lipid mediators released by human platelets after interaction with T. gondii. In addition to TXB2, human platelets after incubation with T. gondii for 90 min released 12-hydroxyheptadecatrienoic acid (12-HHT), 12-hydroxyeicosatetraenoic acid (12-HETE), and an unidentified peak (UVmax 234 nm) as determined by reverse-phase high-performance liquid chromatography. Thermospray-liquid chromatography/mass spectrometry analysis and straight-phase HPLC identified the unknown peak as a mixture of 13-hydroxyoctadecadienoic acid (HODE) and 9-HODE. Radiolabeling studies with [14C]linoleic acid indicated that the platelets were the cellular source of the octadecanoids with 13-HODE (87.7%) greater than 9-HODE (12.3%). Inhibitor studies with indomethacin indicated that 13-HODE was a lipoxygenase product and 9-HODE was a cyclooxygenase product of linoleic acid. Thus, Toxoplasma-stimulated platelets release oxygenated products of both arachidonic acid and linoleic acid which may be important in the host response to T. gondii infection.

Acute toxoplasma myositis: an immunohistochemical and ultrastructural study

The occurrence is reported of acute myositis in a man with meningoencephalitis due to toxoplasmosis. The ultrastructure and immunohistochemistry of a muscle biopsy of the patient were investigated. Toxoplasma organisms were not found in the muscle biopsy. The perivascular inflammatory cells in the muscle were mainly CD4+ T cells and the inflammatory cells in and around the muscle fibres were chiefly macrophages. Expression of major histocompatibility complex class I and II antigens was observed in the infiltrating cells and endothelial cells of the blood vessels. A small proportion of the infiltrating cells expressed interferon-gamma. A possible role of the immune mechanism in the evolution of myositis is discussed.

In vitro and in vivo effects of doxycycline on Toxoplasma gondii

We investigated the effects of doxycycline on Toxoplasma gondii infections in vitro and in vivo. Resident peritoneal macrophages were infected with the virulent RH strain of T. gondii and exposed to doxycycline at different concentrations. The antitoxoplasmic activity of doxycycline was first assessed with [3H]uracil, which is incorporated by the parasite but not the host cell. The concentration of doxycycline that inhibited 50% of the radioactive uptake was calculated to be 6.4 micrograms/ml (95% confidence limits, 5.07 to 8.06 micrograms/ml); the concentration of doxycycline that inhibited 90% of the radioactive uptake was 14 micrograms/ml. Tetracycline was ineffective up to 40 micrograms/ml. Furthermore, microscopic examination of the infected macrophages after treatment with doxycycline confirmed the inhibition of intracellular growth of T. gondii. Mice acutely infected by the intraperitoneal route with 5 x 10(3) tachyzoites of T. gondii were protected against death with a dose of 300 mg of doxycycline per kg (body weight) administered by the oral route for 10 days, starting 24 h after challenge. When mice were infected with 10(5) tachyzoites of T. gondii and treated 12 days starting 2 h after challenge, the protection and the cure rates were, respectively, 100 and 0% after doxycycline alone (300 mg/kg per day), 0 and 0% after pyrimethamine alone (12.5 mg/kg per day), and 100 and 60% after the combination of these two drugs at the same dosages given above. These results suggest that doxycycline may prove to be useful in the treatment of toxoplasmic infections.

Presumed toxoplasmic retinochoroiditis in four siblings

Four siblings in an East Indian family showed typical ophthalmoscopic findings of toxoplasmic retinochoroiditis. Serologic data confirmed exposure to Toxoplasma gondii and the results of other tests excluded other etiologic agents. Three siblings had documented episodes of ocular inflammation consistent with recurrent toxoplasmic retinochoroiditis. The fourth sibling developed a de novo lesion following an illness consistent with systemic toxoplasmosis.

Polymyositis and toxoplasmosis

Extensive severe polymyositis in a patient with toxoplasmosis was presented. Toxoplasmosis was serologically substantiated by a serial two tube rise in a toxoplasma-antibody titer by a hemagglutination test. When appeared to be toxoplasma gondii was detected in areas of myositis. Toxoplasma gondii was found in a single small area of hepatic necrosis, but no other organ or tissue was involved. Thus, the present case was peculiar in respect that skeletal muscles were the major target of toxoplasmosis. A causal relationship between toxoplasmosis and polymyositis was discussed and the literatures were reviewed. Serological investigation and histopathological search for toxoplasma gondii should be done in every case of polymyositis not only for the appropriate therapy but also for the further elucidation of the relationship between toxoplasmosis and polymyositis.

Outbreak of toxoplasmosis in a family and documentation of acquired retinochoroiditis

An outbreak of toxoplasmosis in one household is described. It demonstrates the potential for a common source infection with Toxoplasma gondii to cause multiple cases. Six of seven members of a household investigated for toxoplasmosis demonstrated high antibody titers consistent with recent infection; five of these members (83%) were symptomatic. The most common manifestations were fever and lymphadenopathy, which developed from seven to 18 days (mean 11 days) after a common source ingestion of infected meat. Since inadequately cooked lamb, pork and beef are probably the most common sources of infection in the United States, outbreaks of multiple cases may occur more frequently than is generally appreciated. As more outbreaks of febrile illnesses are examined, especially in families and closed communities, it is likely that more common source epidemics of toxoplasmosis will be recognized. Retinochoroiditis is an unusual manifestation of adult acquired toxoplasmosis. In the index case in this epidemic the patient manifested vision threatening retinochoroiditis 129 days after infection with toxoplasmosis. He represents the ninth well-documented case of toxoplasma retinochoroiditis associated with adult acquired disease.

The relationship and significance of antibody titres as determined by various serological methods in glandular and ocular toxoplasmosis

Three types of antibody curve have been demonstrated by testing sera during the course of acquired toxoplasmosis by six different techniques. These three types are due to cell-wall antibody, (demonstrated by four of the techniques), to antibody to soluble antigen, and to IgM antibody to the cell wall. These findings have been supported by absorption experiments. A scheme is presented for testing single sera by two or three different tests to indicate the stage and duration of the infection.

Toxoplasma encephalitis in a raw steak eater

A case of adult acquired toxoplasma encephalitis is described. The patient was in the habit of eating raw or very lightly cooked steak, and could have obtained her infection from this source.

[ELECTROENCEPHALOGRAPHIC FINDINGS IN PATIENTS WITH TOXOPLASMOSIS]

Foram estudados os exames eletrencefalográficos de 34 pacientes com toxoplasmose, comparando-os com os eletrencefalogramas obtidos em grupo contrôle constituido por 50 indivíduos sem coriorretinite, sem síndrome convulsiva e sem sintomatologia neurológica. Para diferençar traçados eletrencefalográficos normais de traçados alterados foram considerados: a) a presença, ou não, de atividade paroxística focal; b) a freqüência geral da atividade elétrica; c) as assimetrias de ritmo; d) o caráter e grau de resposta à ativação pela hiperpnéia. Alterações eletrencefalográficas foram observadas em 30 (88,2%) pacientes do grupo com toxoplasmose e em 27 (54%) indivíduos do grupo contrôle. Atividade paroxística focal representada por ondas "sharp" foi registrada em 18 (53%) pacientes do grupo patológico: em 7 a alteração foi encontrada no traçado de repouso e confirmada no traçado ativado pela hiperpnéia; em 10 a alteração só foi registrada durante o traçado ativado; em 1, só foi observada durante o traçado de repouso, não tendo sido o paciente submetido à ativação pela hiperpnéia. No grupo contrôle, a atividade paroxística focal foi observada em 8 (16%) indivíduos, sendo que em um a alteração foi registrada durante o traçado de repouso e durante o sono. Ritmos rápidos de mais de 13 c/seg. foram registrados em 5 (15%) pacientes do grupo patológico; no grupo contrôle não foram encontrados ritmos rápidos. Assimetria da atividade elétrica cerebral apareceu em 7 (21,2%) pacientes do grupo patológico e em 3 (6%) do grupo contrôle. Desorganização do ritmo foi encontrada em 15 (46,9%) pacientes do grupo patológico e em 11 (22%) do grupo contrôle, sempre mediante ativação pela hiperpnéia. A desorganização do ritmo, quando encontrada, revelou-se, em média, mais duradoura no grupo patológico que no grupo contrôle. Irregularidade do ritmo foi observada em 12 (37,5%) pacientes do grupo patológico, sendo que em dois foi registrada tanto no traçado de repouso como no ativado pela hiperpnéia e, em 10, só no traçado ativado pela hiperpneia. No grupo controle, a desorganização foi encontrada em 12 (24%) indivíduos, sempre após ativação pela hiperpnéia. Discreta irregularidade só foi encontrada em 3 (6%) dos indivíduos controles, sempre no traçado ativado pela hiperpnéia.