Radiological signs in newborns exposed to primary Toxoplasma infection in utero

Dectin-1 Compromises Innate Responses and Host Resistance against Neospora caninum Infection

Neospora caninum is an intracellular protozoan parasite that has drawn increasing interest due to its association with worldwide repetitive bovine abortions, which cause billionaire losses to the meat and dairy industries annually. Innate immunity plays an important role in infection control, and N. caninum activates the production of inflammatory mediators through toll-like receptors, NOD-like receptors, and mitogen-activated protein kinase signaling pathways. Advances in the knowledge of initial host–parasite interactions are desirable for the design of control measures against the infection, obliterating its pathogenesis. In that sense, we here aimed to describe the role of the innate C-type lectin receptor Dectin-1 during the infection by N. caninum. With that intent, we observed that the absence of Dectin-1, observed in genetically depleted (Dectin-1^−/−) mice or competitively inhibited by an inert agonist [laminarin (LAM)], rescued 50% of the mice infected with lethal doses of N. caninum. Dectin-1^−/− and LAM-treated mice also presented a reduction in the parasite load during acute and chronic phases, associated with decreased inflammatory scores in the central nervous system. Among all the cell phenotypes that migrated to the initial site of infection, dendritic cells and macrophages gained subpopulations with high Dectin-1 surface expression. The impairment of the receptor in these cells led to a decreased parasite burden, as well as augmented production of IL-12p40. We also found that Dectin-1⁺ cells produced less reactive oxygen species (ROS) at the initial site of the infection, while mice deficient in NADPH oxidase isoform 2 (NOX2^−/−) were not able to control parasite replication and produce IL-12p40, even upon LAM treatment. Interestingly, the absence of functional Dectin-1 did not alter the susceptibility of mice against closely related Toxoplasma gondii. In conclusion, the gathered data suggest that Dectin-1 is involved in the parasite-induced downmodulation of ROS, and other key molecules triggered for the control of N. caninum infection and are a promising target for future development of protocols intended for intervention against neosporosis.

Unexpected hosts: imaging parasitic diseases

Radiologists seldom encounter parasitic diseases in their daily practice in most of Europe, although the incidence of these diseases is increasing due to migration and tourism from/to endemic areas. Moreover, some parasitic diseases are still endemic in certain European regions, and immunocompromised individuals also pose a higher risk of developing these conditions. This article reviews and summarises the imaging findings of some of the most important and frequent human parasitic diseases, including information about the parasite's life cycle, pathophysiology, clinical findings, diagnosis, and treatment. We include malaria, amoebiasis, toxoplasmosis, trypanosomiasis, leishmaniasis, echinococcosis, cysticercosis, clonorchiasis, schistosomiasis, fascioliasis, ascariasis, anisakiasis, dracunculiasis, and strongyloidiasis. The aim of this review is to help radiologists when dealing with these diseases or in cases where they are suspected. Teaching Points • Incidence of parasitic diseases is increasing due to migratory movements and travelling. • Some parasitic diseases are still endemic in certain regions in Europe. • Parasitic diseases can have complex life cycles often involving different hosts. • Prompt diagnosis and treatment is essential for patient management in parasitic diseases. • Radiologists should be able to recognise and suspect the most relevant parasitic diseases.

Diagnosis of toxoplasmosis and typing of Toxoplasma gondii

Toxoplasmosis, caused by the obligate intracellular protozoan Toxoplasma gondii, is an important zoonosis with medical and veterinary importance worldwide. The disease is mainly contracted by ingesting undercooked or raw meat containing viable tissue cysts, or by ingesting food or water contaminated with oocysts. The diagnosis and genetic characterization of T. gondii infection is crucial for the surveillance, prevention and control of toxoplasmosis. Traditional approaches for the diagnosis of toxoplasmosis include etiological, immunological and imaging techniques. Diagnosis of toxoplasmosis has been improved by the emergence of molecular technologies to amplify parasite nucleic acids. Among these, polymerase chain reaction (PCR)-based molecular techniques have been useful for the genetic characterization of T. gondii. Serotyping methods based on polymorphic polypeptides have the potential to become the choice for typing T. gondii in humans and animals. In this review, we summarize conventional non-DNA-based diagnostic methods, and the DNA-based molecular techniques for the diagnosis and genetic characterization of T. gondii. These techniques have provided foundations for further development of more effective and accurate detection of T. gondii infection. These advances will contribute to an improved understanding of the epidemiology, prevention and control of toxoplasmosis.

Abordagem diagnóstica e terapêutica da toxoplasmose em gestantes e as repercussões no recém-nascido

OBJETIVO:Avaliar a abordagem diagnóstica e terapêutica da toxoplasmose de gestantes que apresentaram IgM positiva para a doença e o acompanhamento de seus filhos em um hospital público no Rio de Janeiro, RJ. MÉTODOS: Estudo transversal retrospectivo de 2003 a 2006, realizado por meio da análise dos prontuários de 98 gestantes com sorologia IgM positiva para toxoplasmose e seus filhos (99 crianças). O seguimento das crianças com e sem infecção congênita foram analisados, assim como a apresentação clínica daquelas com infecção congênita e os testes diagnósticos utilizados para identificar a infecção pelo Toxoplasma gondii durante a gestação. RESULTADOS: O diagnóstico sorológico foi realizado em 76 pacientes no segundo e terceiro trimestre gestacional. Em 36 gestantes, a determinação dos níveis séricos de IgM foi o único teste diagnóstico realizado para infecção pelo toxoplasma. Em 49 gestantes, os índices de IgM, pela técnica ELFA, foram baixos. O teste de avidez de IgG foi realizado em 62 gestantes e somente 13 o realizaram no primeiro trimestre gestacional. O tratamento específico para toxoplasmose foi empregado em 93 gestantes. A taxa de transmissão vertical foi de 4%. Manifestações clínicas de toxoplasmose congênita foram encontradas em todas as crianças infectadas. Todas as crianças não infectadas apresentaram declínio de IgG específica para toxoplasmose ao longo do acompanhamento ambulatorial; a idade média de IgG comprovadamente negativa nessas crianças foi de 5,4 meses. CONCLUSÕES: Os resultados sugerem que uma sorologia positiva para IgM, como um único marcador sorológico para detectar infecção recente, tem um valor limitado.

Microcephaly: a radiological review

Microcephaly results from inadequate brain growth during development. It may develop in utero, and therefore be present at birth, or may develop later as a result of perinatal events or postnatal conditions. The aetiology of microcephaly may be congenital (secondary to cerebral malformations or metabolic abnormalities) or acquired, most frequently following an ischaemic insult. This distinct radiological and pathological entity is reviewed with a specific focus on aetiology.

Why prevent, diagnose and treat congenital toxoplasmosis?

Evidence that prevention, diagnosis and treatment of toxoplasmosis is beneficial developed as follows: anti-parasitic agents abrogate Toxoplasma gondii tachyzoite growth, preventing destruction of infected, cultured, mammalian cells and cure active infections in experimental animals, including primates. They treat active infections in persons who are immune-compromised, limit destruction of retina by replicating parasites and thereby treat ocular toxoplasmosis and treat active infection in the fetus and infant. Outcomes of untreated congenital toxoplasmosis include adverse ocular and neurologic sequelae described in different countries and decades. Better outcomes are associated with treatment of infected infants throughout their first year of life. Shorter intervals between diagnosis and treatment in utero improve outcomes. A French approach for diagnosis and treatment of congenital toxoplasmosis in the fetus and infant can prevent toxoplasmosis and limit adverse sequelae. In addition, new data demonstrate that this French approach results in favorable outcomes with some early gestation infections. A standardized approach to diagnosis and treatment during gestation has not yet been applied generally in the USA. Nonetheless, a small, similar experience confirms that this French approach is feasible, safe, and results in favorable outcomes in the National Collaborative Chicago-based Congenital Toxoplasmosis Study cohort. Prompt diagnosis, prevention and treatment reduce adverse sequelae of congenital toxoplasmosis.

Agreement between ultrasonography and computed tomography in detecting intracranial calcifications in congenital toxoplasmosis

AIM

To evaluate the agreement between ultrasound (US) and computed tomography (CT) in detecting intracranial calcification in infants with congenital toxoplasmosis.

MATERIALS AND METHODS

Forty-four infants referred for investigation of congenital toxoplasmosis were prospectively evaluated, and the diagnosis was confirmed or ruled out by serological testing and by follow-up in the first year of life. The investigation protocol included cranial US and cranial CT, and examinations were conducted and interpreted by two radiologists blinded to the results of the other imaging test and to the diagnostic confirmation.

RESULTS

The diagnosis of congenital toxoplasmosis was confirmed in 33 patients, and agreement between US and CT findings was found in 31 of these cases. Both methods detected calcifications in 18 patients, and neither detected calcifications in 13 patients. Overall agreement was 94% and the kappa coefficient was 0.88 (95% confidence interval: 0.71, 1; p<0.001), which revealed almost perfect agreement between the two diagnostic methods.

CONCLUSION

In this study, US and CT demonstrated equal sensitivity in the detection of intracranial calcification in infants with congenital toxoplasmosis.

Neonatal lenticulostriate vasculopathy: further characterisation

BACKGROUND

Lenticulostriate vasculopathy (LSV) is sometimes detected on routine brain ultrasonography in neonates, and is often associated with various perinatal and neonatal abnormalities. However, most reports on LSV are retrospective with no controls.

OBJECTIVES

To compare the perinatal and neonatal clinical characteristics of neonates with LSV with matched controls and to summarise all published reports of LSV.

DESIGN

A prospective study that summarises the clinical, laboratory, and neurosonographic data of neonates with LSV.

METHODS

Of 1184 neonates admitted to the neonatal intensive care unit (NICU) during a three year period, 857 had a routine head ultrasound examination. Twenty one had LSV, and were compared with 42 matched controls with regard to gestational, perinatal, neonatal, laboratory, and neurosonographic characteristics.

RESULTS

LSV was detected in 21 of the 857 (2.45%) neonates. It was bilateral in 10 of the 21 cases and located in the thalamus (n = 14) and basal ganglia (n = 7). Infants with LSV were not significantly different from matched controls in most tested variables. However, compared with the control group, the LSV group included significantly more multiple births and more disturbances in amniotic fluid volume, but less meconial amniotic fluid. In addition, the patients with LSV required fewer blood transfusions and less phototherapy.

CONCLUSIONS

Except for more multiple births, neonates with LSV did not display more adverse findings than their matched controls.

Congenital toxoplasmosis

Toxoplasma gondii, a parasite, has three modes of transmission: oral intake of raw or undercooked meat or contaminated fruits and vegetables, ingestion of materials contaminated with cat feces, and transplacental infection. The focus of this article is congenital toxoplasmosis, which is transmitted to the fetus across the placenta. When primary infection of the mother occurs during pregnancy, there is a 40 percent chance of fetal infection; rate of transmission and severity of infection are related to gestational age at the time of infection. The brain and retina are often affected, and there can be a wide range of clinical disease. Amniocentesis or cordocentesis provides the most accurate diagnosis. At birth, 80-90 percent of infants with congenital toxoplasmosis are asymptomatic. But further testing may reveal retinal and central nervous system abnormalities, and there is a risk of long-term sequelae. Chorioretinitis, hydrocephalus, intracranial calcifications, and convulsions are the typical presentation of classic congenital toxoplasmosis. Serology is the most common method of diagnosing neonatal infection, but more complex tests are also utilized. The prognosis for the untreated infant is poor; however, when antibiotic therapy is started early, the rate of sequelae is reduced significantly.

Prenatal diagnosis of congenital toxoplasmosis by duplex real-time PCR using fluorescence resonance energy transfer hybridization probes

The diagnosis of congenital toxoplasmosis frequently relies on PCR tests of amniotic fluid (AF). A duplex real-time quantitative PCR test based on fluorescence resonance energy transfer was developed to quantify the parasite load and to decrease the risk of contamination. An internal control based on the detection of 10 pg mouse DNA added to the AF was included to check for PCR efficiency. The relationship between the parasite load and the occurrence of ultrasonographic abnormalities in 87 samples of AF was analyzed. Seven AF (8%) had a parasitic load > 10(3); 14 (16%) had > 10(2)-< or =10(3); 26 (30%) had > 10-< or = 10(2); and 40 (46%) had < or = 10 parasites/ml. Four of the six AF with cerebral ventriculomegaly had >10(3) parasites/ml. The other two had 130 and 24 parasites/ml, respectively. No parasitic loads of > 10(3) parasites/ml and no ultrasonographic abnormalities were observed in the 11 AF with maternal toxoplasmosis in the third trimester. Therefore, there is a trend to associate high parasite count with ultrasonographic abnormality, but the main concern remains early maternal infection. The importance of quantification should be better evaluated with postnatal studies. The duplex LightCycler PCR test currently provides rapid and safe results.

Toxoplasmosis

Toxoplasmosis is caused by the protozoan organism, Toxoplasma gondii. Infection with this organism primarily results from contact with infected cats and from ingestion of improperly cooked meat. Most adults with toxoplasmosis are asymptomatic. When symptoms are present, they typically resemble a mononucleosis or flulike illness. The diagnosis of toxoplasmosis in the pregnant adult is best made using serological techniques to detect IgM antibody and to document significant changes in the IgG antibody titer. Congenital toxoplasmosis usually occurs as a result of primary maternal infection. The most useful tests for confirmation of fetal infection are ultrasound examination, cordocentesis for detection of IgM-specific antibody, and amniocentesis for detection of toxoplasma DNA in amniotic fluid. Congenital toxoplasmosis can be treated with reasonable success by administration of antibiotics (spiramycin, sulfadiazine, and pyrimethamine) to the mother. In an effort to prevent acquisition of infection, pregnant women should be counseled to avoid contact with cat litter and improperly cooked beef, pork, or lamb.