Neuroparasitic infections: nematodes

Improving the detection of Angiostrongylus cantonensis in the brain tissues of mammalian hosts

Angiostrongylus cantonensis is an invasive nematode parasite that causes eosinophilic meningitis in many vertebrate hosts, including humans. This parasite is spreading rapidly through the six continents, with Europe being the final frontier. Sentinel surveillance may be a cost-effective strategy to monitor the pathogen's arrival to new geographical regions. Necropsy, followed by tissue digestion, is often used to recover helminth parasites from vertebrate host tissues, however, to detect brain parasites, this protocol is poorly utilized. Our brain digestion protocol is easily performed and 1) reduces false positivity and negativity, 2) provides accurate estimates of parasite burden and 3) helps establish a more precise prevalence. Early detection of A. cantonensis increases the efficacy of prevention, treatment, and disease control strategies for susceptible animal populations and humans.

Central Nervous System Infections in the Immunocompromised Adult Presenting to the Emergency Department

Over the past 2 decades, the population of immunocompromised patients has increased dramatically in the United States. These patients are at elevated risk for both community-acquired and opportunistic central nervous system infections. We review the most common and serious central nervous system pathogens affecting these patients and outline a diagnostic and therapeutic approach to their management in the emergency department. We recommend a broad diagnostic evaluation, including neuroimaging and cerebrospinal fluid studies where appropriate, empiric antimicrobial therapy, and early involvement of subspecialists to provide comprehensive care for these complex patients.

Toxocariasis of the Nervous System

PURPOSE

Toxocariasis is a helminthozoonosis caused by the infection of a human host by the larva of Toxocara spp., predominately involving Toxocara canis and Toxocara cati, which are common nematodes in dogs and cats, respectively. Human transmission occurs through contact with animals or by consumption of food contaminated with parasite's eggs. The purpose of this article is to review the current knowledge regarding human neurotoxocariasis.

METHODS

We conducted a systematic review of the existing literature concerning toxocariasis of the nervous system.

RESULTS

Clinical spectrum of human toxocariasis varies widely from a subclinical course to significant organ morbidity. Clinical course depends on parasitic load, the migration route of the larvae and host response. Human neurotoxocariasis is a relatively rare entity yet associated with severe sequelae. Manifestations include meningitis (usually eosinophilic), encephalitis, myelitis, cerebellar vasculitis, space-occupying lesion, behavioral abnormalities, and optic neuritis. Even though valid diagnostic criteria are lacking, neurotoxocariasis should be suspected in patients with neurologic symptoms and cerebrospinal fluid (CSF) pleocytosis with eosinophilia, positive serology for anti-Toxocara antibodies, in serum and/or CSF, sterile CSF and clinical improvement after antihelminthic treatment. Neurotoxocariasis is treated by benzimidazole components, most frequently albendazole, corticosteroids, or diethylcarbamazine.

CONCLUSION

Parasite larvae migrate through tissues and are able to reach the nervous system causing neurotoxocariasis. Its clinical spectrum varies and includes myelitis, meningoencephalitis, brain abscess, and vasculitis. Neurotoxocariasis should always be suspected in patients with neurologic symptoms accompanied by eosinophilia in blood and/or CSF. Early diagnosis and treatment could prevent long-term neurologic impairment.

Sensitivity and specificity of recombinant proteins in Toxocara spp. for serodiagnosis in humans: Differences in adult and child populations

Toxocariasis is a neglected zoonosis that affects children and adults. Recombinant proteins have been widely investigated for diagnosis, achieving high sensitivity and specificity in an overall population; however, little is known about age as a factor in its application. This study aims to investigate the diagnostic potential of Toxocara canis TES-30 and TES-120 recombinant proteins in humans, differentiating between its performance in children and adults. Serum samples collected from children and adults seropositive to Toxocara spp. were tested with indirect ELISA using T. canis TES-30 and TES-120 recombinant proteins produced in Escherichia coli. While rTES-30 sensitivity was not affected by age (81.8% in children and 87% in adults), rTES-120 sensitivity severely decreased in children to only 63.6%, down from 95.7% in adults. Furthermore, the sensitivity of rTES-30 increased to 97.8% after Western blotting confirmation. High specificity (>94%) against other geohelminths was reported for both recombinant proteins. Our study favors the use of rTES-30 with total IgG as the primary antibody in an indirect ELISA assay as a tool for epidemiological human studies.

Case report: a case of diffuse unilateral subacute neuroretinitis (DUSN) in a child

BACKGROUND

Diffuse unilateral subacute neuroretinitis (DUSN) is a rare cause of posterior uveitis in the United Kingdom. It typically presents unilaterally in children and young adults but rarely bilateral cases have been reported. It is also rare to have multiple worms in the same eye causing the clinical picture. In this article, we present a challenging case of DUSN in a young girl unresponsive to conventional treatments suggesting the possibility of multiple worms being present in the same eye.

CASE PRESENTATION

An 8-year-old girl presented with a 2-month history of headaches. On occasions the headaches were associated with redness and watering of her left eye. She denied any visual loss or visual symptoms. Her visual acuity was reduced to 6/30 in her left eye. Fundal examination revealed a unilateral chorioretinitis. Investigation did not reveal a specific cause for the chorioretinitis. Over 15 months her visual acuity improved to 6/9 but the fundal appearance changed and a diagnosis of DUSN was made. She was treated with focal laser, systemic anti-helminthic and immunosuppressive treatments but continued to develop new, active areas of chorioretinitis, raising the possibility of multiple worms in the sub-retinal space. There is also a concern as to other central nervous system (CNS) involvement given her significant and ongoing headaches.

CONCLUSION

We present a challenging case of DUSN in a young girl; a condition that remains rare in the UK. She was unresponsive to both focal laser and systemic anti-helminthic and immunosuppressive treatments suggesting the possibility of multiple worms being present in the sub-retinal space. This case highlights the difficulties often encountered in the treatment of DUSN, even when a worm can be identified. Her visual prognosis is poor as there was ongoing recurrence of active chorioretinitis.

LED based real-time survival bioassays for nematode research

Nematode bioassays are extensively conducted worldwide, either for screening anthelmintic drugs or for assessing the toxicity of drug candidates. Recently, the US Environmental Protection Agency mandated the use of invertebrate models including nematodes especially Caenorhabditis elegans, for toxicity testing as an alternative to rodent models. The significance of nematode bioassays in the biological sciences is escalating, but no standardized protocol is available to assess nematode mortality in a liquid medium. Manual counting under white light is the only approach currently practiced, which exhibit large variabilities and false positive results. Here, we describe an innovative counting strategy that employs light-emitting diode (LED) technology. We found that the nematodes stopped moving under white light (360–760 nm) when administered with sub-lethal dosage (LC₅₀) of a toxic drug, whereas they responded rapidly to blue (450–490 nm) and ultraviolet (UV) (100–400 nm) LED lights. Furthermore, paralyzed nematodes responded in less than 5 seconds to a LED pulse. The response to the LED stimulus was distinctively noted in C. elegans dauers, which squirmed away from illuminated sites within seconds. LED produced an incoherent beam, and uniformly distributed light across the sampling area. In conclusion, this method is more accurate than the conventional counting techniques, and enables us to differentiate paralyzed and dead nematodes virtually in real-time. Furthermore, this technique would appear to be suitable for incorporating a motion-sensor based automated system.

Nematode eggs observed in cytology of cerebrospinal fluid diagnostic for intramedullary Spirocerca lupi spinal cord migration

Spinal spirocercosis due to aberrant Spirocerca lupi nematode migration is an emerging etiology for acute myelitis in dogs in Israel, causing severe, mostly nonsymmetrical hind limb paresis or paralysis, and sometimes tetraparesis or tetraparalysis. So far, incidental identification of parasites during spinal surgery or at necropsy provides the only definite diagnosis, while antemortem diagnosis of this condition has been uncertain. Specifically, antemortem diagnosis is based on the typical clinical presentation of acute, progressive, asymmetrical hind limb paresis or paralysis, with moderate to severe eosinophilic to mixed cerebrospinal fluid (CSF) pleocytosis and increased CSF protein concentration. Exclusion of other differential diagnoses also requires using spinal cord imaging. In this novel report, we document a case of an intradural spinal spirocercosis in a dog, diagnosed antemortem, by detecting S lupi eggs in the CSF, and subsequent treatment, resulting in the resolution of the clinical signs.

Hepatic visceral larva migrans, a resilient entity on imaging: Experience from a tertiary liver center

INTRODUCTION

Hepatic visceral larva migrans (VLM) is an uncommon parasitic manifestation seen in the liver. It presents as coalescing, conglomerated, or solitary abscess cavities in the liver on imaging. We conducted a retrospective clinico-radiological analysis of 24 patients with biopsy proven VLM who were reviewed and followed up at our tertiary liver institute over a period of 4 years.

MATERIALS AND METHODS

The study was performed to correlate the radiological features and imaging response to therapy for hepatic VLM. The disease course, imaging findings, progressive, absolute eosinophil counts (AEC), hydatid serology, and the extent of radiological regression of the liver lesions, on follow-up were analyzed.

RESULTS

Imaging showed a diagnostic accuracy of 42%. Hydatid serology was positive in 46% patients before starting treatment. The median pretreatment AEC of 507 showed a significant posttreatment AEC decline to median value of 117. The Wilcoxon signed ranks test showed significant decline in the AEC (P < 0.001). Radiological regression was present in all lesions. However, patients showed residual abscesses on imaging, up to 2 years on follow-up.

CONCLUSION

This study reveals that AEC has a significant predictive value in diagnosis and as a marker for disease regression. Complete radiological resolution of hepatic lesions does not correlate with total clinical remission. This finding warrants the need for further studies to look into the role of prolonged medical therapy or surgery as an alternate to current therapy module in cases of hepatic visceral larva abscesses.

Lack of Association between Toxocara Exposure and Suicide Attempts in Psychiatric Patients

Infection with Toxocara may affect the central nervous system. A high seroprevalence of Toxocara infection has been reported in psychiatric patients. To the best of our knowledge, there is no previous report about an association of Toxocara infection with suicide attempts. Therefore, we sought to determine whether Toxocara exposure is associated with suicide attempts in psychiatric patients. We studied 282 psychiatric outpatients (156 with suicide attempts and 126 without suicide attempts). Sera of patients were analyzed for the presence of anti-Toxocara IgG antibodies by using a commercially available enzyme immunoassay. One of the 156 (0.6%) suicide attempters and 1 (0.8%) of the 126 controls were positive for anti-Toxocara IgG antibodies (OR = 0.80; 95% CI: 0.04–13.02; P = 1.00). Toxocara seropositivity was significantly higher (P = 0.01) in male patients with consumption of raw dried goat meat than male patients without this consumption. Results suggest that Toxocara exposure is not associated with suicide attempts in psychiatric outpatients in Durango City, Mexico. However, further studies with larger samples sizes to confirm our results should be conducted. Too few patients were seropositive to assess further associations of Toxocara exposure with sociodemographic, clinical, and behavioral characteristics of the psychiatric patients.

Toxocara cati larvae in the eye of a child: a case report

Toxocariasis is a consequence of human infection by Toxocara larvae. There are symptomatic (visceral, ocular) and asymptomatic course of toxocariasis. The ocular form is very rare. We present a 6-year-old patient who developed an ocular form of toxocariasis caused by Toxocara cati. He demonstrated lesions in the peripheral retina of the right eye. White granuloma was present in the superior peripheral retina. A positive immunological assay for toxocariasis essentially completed the outcomes. On the basis of clinical manifestations and conducted examinations, a diagnosis of ocular form of toxocariasis was established. Albendazole and corticosteroids were applied in treatment. Current results clearly highlight the usefulness of excretory-secretory antigens derived from larvae of Toxocara cati for the fine diagnosis ocular larva migrans caused by Toxocara larvae.

Rickettsiae, protozoa, and opisthokonta/metazoa

Rhizobiales (formerly named Rickettsiales) cause in rare instances meningitis and meningovasculitis, respectively. In case of history of exposure, infection by Rhizobiales needs to be considered since both diagnosis and therapy may be extremely difficult and pathogen-specific. The same applies to protozoa; in this chapter, Babesia species, free-living amoebae and Entamoeba histolytica infection, including severe meningitis and brain abscess, infection by Trypanosoma species (South American and African trypanosomiasis) are discussed with respect to history, epidemiology, clinical signs, and symptoms as well as differential diagnosis and therapy. Parasitic flatworms and roundworms, potentially able to invade the central nervous system, trematodes (flukes), cestodes (in particular, Cysticercus cellulosae), but also nematodes (in particular, Strongyloides spp. in the immunocompromised) are of worldwide importance. In contrast, filarial worms, Toxocara spp., Trichinella spp., Gnathostoma and Angiostrongylus spp. are seen only in certain geographically confined areas. Even more regionally confined are infestations of the central nervous system by metazoa, in particular, tongue worms (=arthropods) or larvae of flies (=maggots). The aim of this chapter is (1) to alert the neurologist to these infections, and (2) to enable the attending emergency neurologist to take a knowledgeable history, with an emphasis on epidemiology, clinical signs, and symptoms as well as therapeutic management possibilities.

PCR-based molecular characterization of Toxocara spp. using feces of stray cats: a study from Southwest Iran

Feces of stray cat are potential sources of gastrointestinal parasites and play a crucial role in spreading and transmitting parasite eggs, larvae, and oocysts through contamination of soil, food, or water. In this study, we investigated the prevalence of Toxocara spp. infection in stray cats in Ahvaz city, southwest Iran. Eggs of Toxocara spp. in feces of stray cats were detected by the sucrose flotation method, and identification was conducted by polymerase chain reaction (PCR) and DNA sequencing. Of the 140 fecal samples that were randomly collected from public environments during the months of January to May 2012, 45% were found to harbour Toxocara spp. eggs. The highest prevalence of Toxocara spp. eggs was found in the central area of Ahvaz city (28.6%). T. canis eggs were found in 4 (6.34%) of the 63 positive samples. Stray cats are found in parks, playgrounds, and other public places and may be a potential contamination risk. Identification of Toxocara spp. using molecular methods is sufficiently sensitive to detect low levels of parasites and identify the different Toxocara spp. in feces. The relatively high prevalence of Toxocara spp. infection may continue to increase due to lack of effective environmental hygiene control in Iran. Consequently, there is a need to plan adequate programs to detect, identify, and control this infection as well as stray cats in the region.

Clinical use of anti-TNF therapy and increased risk of infections

Biologics such as antitumor necrosis factor (anti-TNF) drugs have emerged as important agents in the treatment of many chronic inflammatory diseases, especially in cases refractory to conventional treatment modalities. However, opportunistic infections have become a major safety concern in patients on anti-TNF therapy, and physicians who utilize these agents must understand the increased risks of infection. A literature review of the published data on the risk of bacterial, viral, fungal, and parasitic infections associated with anti-TNF therapy was performed and the clinical presentation, diagnostic tests, management, and prevention of opportunistic infections in patients receiving anti-TNF therapy were reviewed. Awareness of the therapeutic potential and associated adverse events is necessary for maximizing therapeutic benefits while minimizing adverse effects from anti-TNF treatments. Patients should be adequately vaccinated when possible and closely monitored for early signs of infection. When serious infections occur, withdrawal of anti-TNF therapy may be necessary until the infection has been identified and properly treated.

Parasitic infections in HIV infected individuals: diagnostic & therapeutic challenges

After 30 years of the human immunodeficiency virus (HIV) epidemic, parasites have been one of the most common opportunistic infections (OIs) and one of the most frequent causes of morbidity and mortality associated with HIV-infected patients. Due to severe immunosuppression, enteric parasitic pathogens in general are emerging and are OIs capable of causing diarrhoeal disease associated with HIV. Of these, Cryptosporidium parvum and Isospora belli are the two most common intestinal protozoan parasites and pose a public health problem in acquired immunodeficiency syndrome (AIDS) patients. These are the only two enteric protozoan parasites that remain in the case definition of AIDS till today. Leishmaniasis, strongyloidiasis and toxoplasmosis are the three main opportunistic causes of systemic involvements reported in HIV-infected patients. Of these, toxoplasmosis is the most important parasitic infection associated with the central nervous system. Due to its complexity in nature, toxoplasmosis is the only parasitic disease capable of not only causing focal but also disseminated forms and it has been included in AIDS-defining illnesses (ADI) ever since. With the introduction of highly active anti-retroviral therapy (HAART), cryptosporidiosis, leishmaniasis, schistosomiasis, strongyloidiasis, and toxoplasmosis are among parasitic diseases reported in association with immune reconstitution inflammatory syndrome (IRIS). This review addresses various aspects of parasitic infections in term of clinical, diagnostic and therapeutic challenges associated with HIV-infection.

Toxocariasis presenting as encephalomyelitis

We describe a farmer who presented with a clinical picture of a transverse thoracic myelitis. MRI showed inflammatory lesions in brain and thoracic spinal cord. Toxocariasis was suspected because of eosinophilia in blood and cerebrospinal fluid, and this diagnosis was confirmed immunologically. He was successfully treated with antihelminthics in combination with corticosteroids. Neurotoxocariasis is rare and diagnosis can be difficult because of the different and atypical clinical manifestations. It should be considered in every case of central neurological syndrome associated with eosinophilia.

Migratory route of Strongyloides venezuelensis in Lewis rats: comparison of histological analyses and PCR

Strongyloides venezuelensis is a parasitic nematode that has been used as a model to study human and animal strongyloidiasis. In this study, we compared the sensitivity between traditional methodologies and PCR assay to characterize the dynamics of S. venezuelensis infection and its migration route in Lewis rats subcutaneously infected with 4000 L3. The dynamics of the infection was determined by counting the number of eggs and by detecting parasite deoxyribonucleic acid in faeces samples. Both techniques similarly detected the infection at day 6 after larvae inoculation. However, PCR performed with the genus primer showed higher sensitivity during the recovery phase. Histological analysis and PCR assay were then used to follow parasite tissue migration. S. venezuelensis migration route included the muscular fibers below the skin, the pulmonary alveoli and the small intestine vilosities. The sensitivity of these two techniques to detect parasite's presence in these tissues was statistically similar.

Emerging zoonoses in the southern United States: toxocariasis, bovine tuberculosis and southern tick-associated rash illness

The majority of emerging diseases in humans have been linked to zoonotic pathogens originating in domestic animals or wildlife. This is a public health concern because zoonotic infections affect several aspects of the society. The complex interactions among pathogen, host and environment also pose challenges in estimating the true burden of those infections. However, the recent development of new molecular diagnostic tools has allowed for better diagnosis of zoonotic infections. This review focuses on 3 emerging zoonoses, namely toxocariasis, bovine tuberculosis and southern tick-associated rash illness, and demonstrates that these infections may be more prevalent in the southern United States than previously recognized. This review places special emphasis on the recent epidemiologic trends, intra/interspecies transmission and clinical features of each of these zoonoses. In addition, treatment and prevention for each zoonotic pathogen are discussed. Clinicians working in the southern United States should be aware of the presence of those zoonotic infections.

Helminthic invasion of the central nervous system: many roads lead to Rome

Invasion of the central nervous system (CNS) by parasitic worms often represents most severe complication of human helminthiasis. The pathways from the portal of entry to the CNS are manifold and differ from species to species. In this mini-review, we analysed the contemporary knowledge and current concepts of the routes pathogenic helminths take to gain access to brain, spinal cord and subarachnoid space.

The role of Onchocerca volvulus in the development of epilepsy in a rural area of Tanzania

INTRODUCTION

Several reports indicate high prevalences of both onchocerciasis and epilepsy in some regions of Africa. This raises the question of whether these diseases are associated. We therefore investigated people with epilepsy and/or onchocerciasis living in an area in Tanzania endemic for Onchocerca volvulus (O. volvulus).

METHODS

We collected clinical information, skin snips, and blood from 300 individuals, and cerebrospinal fluid (CSF) from 197. Participants were allocated to 4 groups consisting of people with epilepsy and onchocerciasis (n=135), those with either epilepsy (n=61) or onchocerciasis only (n=35), and healthy individuals (n=69). Samples were evaluated for microfilaria, IgG4 antibodies against O. volvulus, O. volvulus antibody index (CSF/serum), and CSF routine parameters. Polymerase chain reaction (PCR) was performed on skin snips and CSF.

RESULTS

No difference was found in microfilarial density between participants with and without epilepsy (P=0.498). The antibody index was raised in 2 participants. CSF PCR was negative in all samples tested.

DISCUSSION

Our results do not give evidence of a relationship between O. volvulus and epilepsy. Despite the fact that 2 participants had raised antibody index, the existence of cerebral onchocerciasis caused by migration of microfilariae into the CSF appears unlikely. However, to date unexplored reactions to the infestation with O. volvulus causing epilepsy cannot be excluded.

Verminous Myelitis in a Pit Bull Puppy

A 10-week-old, male pit bull dog presented to the referring veterinarian with hind limb paresis and epaxial muscle atrophy. No spinal lesions were identified at gross necropsy; however, histologically there was marked granulomatous myelitis in the spinal cord between T13 and L2 with occasional, intralesional nematode larvae. Based on morphologic characteristics, the nematode larvae were identified as Strongyloides spp., possibly Strongyloides stercoralis.

Contracaecum sp. infection in Hoplias malabaricus (moncholo) from rivers and marshes of Colombia

Nematode infection indices were recorded in Hoplias malabaricus captured in six different rivers and a marsh belonging to the North Coast Basin of Colombia, and from the Amazon River, during February 2003-December 2004. Preliminary morphological analysis of nematodes indicated the presence of Contracaecum sp. Parasites were mostly found in the intestinal mesenteries and a very low percentage in muscle. Parasite prevalence in all sampling locations at the north of Colombia was 100%, whereas in the Amazon River it was 6.12%. The mean intensity in the different stations were as follows: Magdalena River at the City of Magangué (58.92+/-7.59), Magdalena river at the city of Zambrano (128.9+/-7.08), Sinú River (53.88+/-4.92), Dique Channel (207.3+/-59.52), Cauca River (77.26+/-9.35), Atrato River (21.11+/-2.6), San Jorge River (39.5+/-7.13), and Totumo Marsh (62.5+/-6.38). In average, all specimens of Hoplias malabaricus from the north coast basin of Colombia were infected with a mean intensity of 77.82+/-4.81 (1-466 parasites per host) whereas in fish from the Amazon River this value was significantly lower (intensity 1.0+/-0.0). Size and weight correlated significantly with parasite intensity in fish collected from sampling locations at the north of Colombia (R=0.240, P<0.001 and R=0.199, P=0.008, respectively). Moreover, a significant, but low and negative correlation was found between condition factor and parasite intensity (R=-0.159, P=0.034), suggesting a possible impact of parasites on fish health. These results suggest, for the first time, that the parasitism in Moncholo is a widespread phenomenon in Colombian rivers and could represent a risk factor for human consumers.