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Background The onset of anthelmintic treatment of neurocysticercosis (NCC) provokes an acute immune response of the host, which in human cases is associated with exacerbation of neurological symptoms. This inflammation can occur at the first days of therapy. So, changes in the brain cysts appearance may be detected by medical imaging. We evaluated radiological changes in the appearance of brain cysts (enhancement and size) on days two and five after the onset of antiparasitic treatment using naturally infected pigs as a model for human NCC. Methods and results Contrast T1-weighted magnetic resonance imaging with gadolinium was performed before and after antiparasitic treatment. Eight NCC-infected pigs were treated with praziquantel plus albendazole and euthanized two (n = 4) and five (n = 4) days after treatment; another group of four infected pigs served as untreated controls. For each lesion, gadolinium enhancement intensity (GEI) and cyst volume were measured at baseline and after antiparasitic treatment. Volume and GEI quantification ratios (post/pre-treatment measures) were used to appraise the effect of treatment. Cysts from untreated pigs showed little variations between their basal and post treatment measures. At days 2 and 5 there were significant increases in GEI ratio compared with the untreated group (1.32 and 1.47 vs 1.01, p = 0.021 and p = 0.021). Cyst volume ratios were significantly lower at days 2 and 5 compared with the untreated group (0.60 and 0.22 vs 0.95, p = 0.04 and p = 0.02). Cysts with lower cyst volume ratios showed more marked post-treatment inflammation, loss of vesicular fluid and cyst wall wrinkling. Conclusion/Significance A significant and drastic reduction of cyst size and increased pericystic enhancement occur in the initial days after antiparasitic treatment as an effect of acute perilesional immune response. These significant changes showed that early anthelmintic efficacy (day two) can be detected using magnetic resonance imaging., Author summary Neurocysticercosis (NCC) is a frequent parasitic infection of the human brain and the most common cause of adult onset epilepsy in developing countries. Acute inflammatory response in NCC plays an important role in the pathogenesis of symptoms by anthelminitic therapies. The anthelmintic recommended therapy for NCC has drawbacks as the exacerbation of inflammation around degenerating cysts provokes the appearance of symptoms at the first days of treatment. Radiological changes in the appearance of cysts usually are seen after months of therapy. To evaluate if significant radiological changes (enhancement and size) occur in the first days of therapy, we used a porcine NCC model and magnetic resonance imaging (MRI) with contrast solution. The major radiological changes observed after treatment with albendazole and praziquantel were an increase in enhancement and the significant reduction in cyst size by day 2 and more evident on day 5. Cysts with greater changes also experienced exacerbated inflammation, loss of vesicular fluid and wrinkling of the cyst wall. These results show an early therapeutic effect and the possible utility of repeat MRI imaging within a few days after starting treatment. Finally, these findings contribute to our understanding of the treatment induced early exacerbation of symptoms.

Background Disease manifestations in neurocysticercosis (NCC) are frequently due to inflammation of degenerating Taenia solium brain cysts. Exacerbated inflammation post anthelmintic treatment is associated with leakage of the blood brain barrier (BBB) using Evans blue (EB) staining. How well EB extravasation into the brain correlates with magnetic resonance imaging (MRI) using gadolinium (Gd) enhancement as a contrast agent and pericystic inflammation was analyzed in pigs harboring brain cysts of Taenia solium. Methodology/Principal Findings Three groups of 4 naturally infected pigs were assessed. The first and second groups were treated with both praziquantel plus albendazole and sacrificed two and five days post treatment, respectively. A third untreated group remained untreated. Pigs were injected with EB two hours prior to evaluation by Gd-enhanced T1-MRI, and euthanized. The EB staining for each cyst capsule was scored (EB grades were 0: 0%; 1: up to 50%; 2: over 50% but less than 100%; 3: 100%). Similarly, the Gd enhancement around each cyst was qualitatively and quantitatively scored from the MRI. The extent of pericystic inflammation on histology was scored in increasing severity as IS1, IS2, IS3 and IS4. Grade 3 EB staining and enhancement was only seen in treated capsules. Also, treated groups had higher Gd intensity than the untreated group. Grades of enhancement correlated significantly with Gd enhancement intensity. EB staining was correlated with Gd enhancement intensity and with IS4 in the treated groups. These correlations were stronger in internally located cysts compared to superficial cysts in treated groups. Significance EB staining and Gd enhancement strongly correlate. The intensity of enhancement determined by MRI is a good indication of the degree of inflammation. Similarly, EB staining highly correlates with the degree of inflammation and may be applied to study inflammation in the pig model of NCC., Author Summary Neurocysticercosis (NCC) is a frequent parasitic infection of the human brain in developing countries. The symptomatology of human NCC after antiparasitic treatment is generally related to inflammation. The presence and degree of enhancement after intravascular injection of the contrast agent gadolinium in magnetic resonance imaging (MRI) is commonly considered an evidence of blood brain barrier (BBB) leakage. Experimentally, the presence and degree of extravasation of Evans blue (EB) after intravascular injection into the tissues of the brain is a direct measure of blood brain barrier leakage. The BBB leakage of gadolinium in neurocysticercosis is commonly used as an indirect measure of inflammation but has never been experimentally proven. Here we evaluated the relationship between contrast T1-MRI, EB staining and histology findings in naturally infected pigs. There was a strong correlation between EB staining, contrast MRI and histopathology findings after antiparasitic treatment. This correlation was stronger when cysts were internally located in the brain than in superficial cysts partly located in the subarachnoid space (meninges). Contrast-enhanced MRI is a non invasive tool used in diagnosis and follow up of NCC patients. This study shows that the use of EB staining allows for the same conclusions as when using MRI post-treatment, and that both techniques correlate with histopathology findings. These results support the use of EB staining to study NCC using the porcine model as well as validate MRI enhancement to assess brain inflammation in patients.

Cysticidal treatment of neurocysticercosis, an infection of humans and pig brains with Taenia solium, results in an early inflammatory response directed to cysts causing seizures and focal neurological manifestations. Treatment-induced pericystic inflammation and its association with blood brain barrier (BBB) dysfunction, as determined by Evans blue (EB) extravasation, was studied in infected untreated and anthelmintic-treated pigs. We compared the magnitude and extent of the pericystic inflammation, presence of EB-stained capsules, the level of damage to the parasite, expression of genes for proinflammatory and regulatory cytokines, chemokines, and tissue remodeling by quantitative PCR assays between treated and untreated infected pigs and between EB-stained (blue) and non stained (clear) cysts. Inflammatory scores were higher in pericystic tissues from EB-stained cysts compared to clear cysts from untreated pigs and also from anthelmintic-treated pigs 48 hr and 120 hr after treatment. The degree of inflammation correlated with the severity of cyst wall damage and both increased significantly at 120 hours. Expression levels of the proinflammatory genes for IL-6, IFN-γ, TNF-α were higher in EB-stained cysts compared to clear cysts and unaffected brain tissues, and were generally highest at 120 hr. Additionally, expression of some markers of immunoregulatory activity (IL-10, IL-2Rα) were decreased in EB-stained capsules. An increase in other markers for regulatory T cells (CTLA4, FoxP3) was found, as well as significant increases in expression of two metalloproteases, MMP1 and MMP2 at 48 hr and 120 hr post-treatment. We conclude that the increase in severity of the inflammation caused by treatment is accompanied by both a proinflammatory and a complex regulatory response, largely limited to pericystic tissues with compromised vascular integrity. Because treatment induced inflammation occurs in porcine NCC similar to that in human cases, this model can be used to investigate mechanisms involved in host damaging inflammatory responses and agents or modalities that may control damaging post treatment inflammation., Author Summary Neurocysticercosis is caused by infection of the brain with the larval (cyst) stage of the tape worm Taenia solium in humans and pigs. Antiparasitic drug treatment is compromised by worsening of neurological symptoms during therapy due to reactive inflammation triggered by the dying parasite. The immune mechanisms that cause this inflammation are poorly understood. In this study, we investigated the nature of inflammation after treatment in pigs naturally infected with T. solium cysts. Evans blue dye injected into infected pigs marks areas in the brain where the normally impermeable capillaries have become more permeable, allowing damaging cells and molecules to leak out into the brain. By microscopy and measurement of gene expression for inflammation-inducing immune mediators, we show that inflammation in the brain tissues around cysts is more severe with increased vessel leakage. Furthermore, the levels of these mediators increased after antiparasitic drug treatment. A significant implication of these findings is that it may be possible to inhibit the inflammation around parasites using drugs or biologics that inhibit these inflammatory pathways and, thereby, reduce local brain damage during treatment. These observations may also be applicable to other inflammatory conditions that affect the brain.

Neurocysticercosis (NCC) is the most common cause of adult-acquired epilepsy worldwide and one the most frequent parasitic infections associated with chronic morbidity in the United States. Despite its importance [1]–[4], worldwide morbidity due to NCC is underappreciated and research is underfunded, and therefore researchers are unable to capitalize on recent advances that hold great promise to prevent millions of cases of epilepsy and to effectively treat viable brain infections.

Neurocysticercosis (NCC) is an infection of the central nervous system caused by the larval form of the tapeworm Taenia solium. Infections occur following the accidental ingestion of tapeworm ova found in human feces. NCC is a major cause of epilepsy and disability in many of the world's poorer countries where families raise free-roaming pigs that are able to ingest human feces. It is frequently diagnosed in immigrant populations in the United States and Canada, reflecting the high endemicity of the infection in their countries of origin [1]. Although parenchymal cysts are the most common location in the brain and cause seizures, cysts may also be present in the ventricles, meninges, spinal cord, eye, and subarachnoid spaces. Involvement in these other sites may result in aberrant growth (racemose cysts) and complicated disease that is difficult to treat and may cause increased morbidity and mortality. Until recently, NCC and echinococcosis were referred to as “neglected” diseases, but are now recognized by the World Health Organization (WHO) as “major neglected diseases” [2]. In many endemic communities, NCC is the cause of epilepsy in ≥1% of the population. Here, we provide an update of the importance of NCC, recent epidemiological observations, and an outline of the goals of a recently formed group of physicians, the North American Neurocysticercosis Clinical Research Consortium (NACC). NCC is difficult to identify and treat. Diagnosis requires brain imaging, a technology commonly unavailable in resource-poor areas, and clinical diagnosis is unreliable, as the manifestations are diverse and non-specific. Additionally, treatment commonly involves weeks to months of medication with close monitoring for side effects and serial brain imaging. NCC is a significant health problem in Latin American countries (LAC), Haiti, sub-Saharan Africa (SSA), India, Southeast Asia, China, Indonesia, and other regions less well categorized, such as New Guinea and Eastern Europe [2]. Although accurate estimates of the extent of infection and disease are not available for most endemic regions, many studies suggest a higher prevalence of infection and disease burden than has been appreciated by experts [3], [4]. Conventional diagnosis of NCC requires a compatible clinical history, positive serology, and typical computed tomography (CT) or magnetic resonance imaging (MRI) [5]. Determination of the prevalence of infection is hampered by variable sensitivity and specificity of each of the diagnostic tests, which identify a limited or overlapping proportion of the “true” prevalence of infection. For instance, the sensitivity of the serum electroimmunotransfer blot decreases dramatically in those with calcified disease or a single parenchymal cyst [6] and may be falsely positive in persons exposed but not infected. Better estimates of infection can be obtained by imaging of the brain to ensure inclusion of individuals with NCC infection who are asymptomatic and seronegative to T. solium (see Box 1). One study in Peru that characterized prevalence of infection and NCC using a combination of CT imaging, positive serology, and history of seizures to identify infections [7] reported an NCC seroprevalence of 24%. An additional 13% of those with negative serology had CT scans demonstrating calcifications typical of NCC. Adding the observed proportion of seropositive individuals to seronegative individuals with CT imaging evidence of NCC yields an overall prevalence of cysticercosis of 37%. Even this substantial proportion of infection likely underestimates its prevalence in this population. Applying similar calculations to earlier comparable studies performed in Ecuador [8], Honduras [9], and Mexico [10] yields prevalence estimates of infection of 23%, 38%, and 15%, respectively. Therefore, estimates of prevalence as defined in LAC range between 15% and 38%. Applying these prevalence calculations to the 75 million persons at risk in LAC found in 1993 [11] we estimate between 11 and 29 million persons have cysticercosis in LAC. Thus, the burden of infection with cysticercosis and NCC is substantial, and likely higher in absolute numbers with the increasing population currently at risk. These numbers also allow a more appropriate comparison between prevalence estimates of other common infections in LAC [3]. Box 1. Terms Used in This Manuscript Infection: Any or all of the following: Evidence of prior ingestion of T. solium ova resulting in aborted development and positive antibody response, presence of viable or degenerated dead T. solium cysts anywhere in the body irrespective of antibody response. Includes a positive serology for antibodies or antigen, calcifications in brain or muscle, or viable or degenerating parasites. Seroprevalence: Usually a defined population testing positive for antibodies to T. solium cysts. Less commonly positive for cestode antigen in serum. Neurocysticercosis: Evidence of T. solium infection of the brain with or without symptoms. Our estimate of the prevalence of NCC in LAC is substantially higher than that suggested by Bern et al. [11], which estimated symptomatic NCC only, using fairly conservative assumptions. An estimate of mostly active epilepsy was determined by Bern et al. by subtracting the epilepsy rates in non-endemic regions from rates in endemic regions in Peru [11]. Extrapolating to the 1993 population at risk and adjusting for disease other than seizures, the authors calculated that 400,000 individuals in LAC had symptomatic NCC. More recent studies using direct determinations of active epilepsy due to NCC from active epilepsy rates ranging from 0.6% to 1.8% suggest that between 450,000 and 1.35 million persons suffer from epilepsy due to NCC in LAC (Table 1). Table 1 Estimated Numbers of Persons Infected with Neurocysticercosis or Epilepsy due to Neurocysticercosis by Region. Similar to Latin America, many areas of Asia are endemic for NCC. Studies in endemic regions of India reveal high burdens of infection and symptomatic NCC [2]. In a community study in southern India, the seroprevalence of T. solium infection was 15.9%, active epilepsy was present in 3.83/1,000 persons, and 28.4% of these individuals had NCC detected by CT imaging. Extrapolating these figures to the overall population in India suggests that approximately 1 million cases of epilepsy are due to NCC [12]. Cysticercosis is also highly endemic in southwest China. According to a recent WHO report, the average prevalence of T. solium infection in China was 0.11% (range, 0.05%–15%); the estimated number of patients with taeniasis was 1.26 million; and the estimated number of cysticercosis cases was 3–6 million [2]. Although SSA is among the least studied regions, accumulating evidence suggests highly endemic transmission with significant symptomatic disease. High prevalence in pigs in many areas suggests a high level of human taeniasis [13], [14]. Serologic studies suggest many regions of SSA have endemic infection that likely affects large proportions of the population (Table 2 - adapted from Winkler et al. [4]). Epilepsy prevalence in SSA ranges from 5.2 to 74.4 per 1,000 persons. A recent systematic analysis of the proportion of epilepsy endemic regions due to NCC was estimated at 29% (95% CI: 22.9–35.5) [15]. Using this figure, the prevalence of seizures due to NCC in SSA would be 1.7–24.8 per 1,000 persons. Table 2 Serologic Studies of Human Cysticercosis/Neurocysticercosis in Sub-Saharan Africa. Reports of NCC in the United States and Canada have also been increasing over the past 50 years, and these reports mostly reflect disease in Hispanic immigrants [1], [16]–[18]. Regional estimates in the general population range from 0.2 to 0.6 per 100,000 in Oregon and Los Angeles [18], [19]. Of those presenting to urban emergency departments because of seizures, 2.1% were attributable to NCC [18], similar to the proportion of seizure patients with NCC (2%) in Houston [16]. This population also presents with complicated subarachnoid disease, or racemose cysticercosis, which is characterized by cysts that proliferate, enlarge, and develop membranes in the subarachnoid spaces of the brain, mostly involving the basilar cisterns and spine. Sequelae include hydrocephalus, arachnoiditis, infarction, and entrapment syndromes requiring long-term corticosteroids, anthelminthics, and serial imaging. These individuals are frequently referred to tertiary care centers where they may be under the care of NACC participants. Recognizing the importance of NCC in immigrant communities from endemic regions in North America, a group of infectious disease and travel medicine practitioners have come together to focus efforts on management of NCC. The goals of the NACC are to disseminate information regarding diagnosis and treatment of NCC, highlight areas of research need, and advance knowledge through retrospective and prospective collaborative studies of treatment for the more complicated forms of NCC. Initially, we are developing standardized methods to evaluate neuroimaging and morbidity and hope to develop guidelines for treatment. In summary, recent carefully performed studies of the prevalence and burden of disease have recognized NCC as a major cause of epilepsy in endemic regions and a cause of complicated brain disease in immigrant populations. Resources directed at defining high prevalence regions, preventing infection, and treating epilepsy and other complications, all achievable with present technology, and would reduce the burden of this debilitating disease worldwide.