Parasitic worms of the central nervous system: an Australian perspective

Abstract
The diagnosis and management of parasitic diseases of the central nervous system (CNS) is difficult, even for infectious diseases physicians and neurologists. Furthermore, few overviews of the spectrum of causative helminths and clinical syndromes have been published. In the present study, we review the seven most common parasitic diseases of the CNS: (i) cysticercosis, (ii) neuroschistosomiasis, (iii) paragon­imiasis, (iv) angio-strongyliasis, (v) hydatid disease, (vi) sparganosis and (vii) gnathostomiasis. Major syndromes of parasitic disease of the CNS and their differential causes are discussed, including: (i) cystic lesions, (ii) enhancing granulomas (with and without creeping subcutaneous eruptions), (iii) eosinophilic meningoencephalitis and (iv) spinal cord disease. Specific risk factors that predispose to these infections are also discussed and particular attention is drawn to the situation in Australia. (Intern Med J 2002; 32: 541−553)     

Host population persistence in the face of introduced vector-borne diseases: Hawaii amakihi and avian malaria

The past quarter century has seen an unprecedented increase in the number of new and emerging infectious diseases throughout the world, with serious implications for human and wildlife populations. We examined host persistence in the face of introduced vector-borne diseases in Hawaii, where introduced avian malaria and introduced vectors have had a negative impact on most populations of Hawaiian forest birds for nearly a century. We studied birds, parasites, and vectors in nine study areas from 0 to 1,800 m on Mauna Loa Volcano, Hawaii from January to October, 2002. Contrary to predictions of prior work, we found that Hawaii amakihi (Hemignathus virens), a native species susceptible to malaria, comprised from 24.5% to 51.9% of the avian community at three low-elevation forests (55-270 m). Amakihi were more abundant at low elevations than at disease-free high elevations, and were resident and breeding there. Infection rates were 24-40% by microscopy and 55-83% by serology, with most infected individuals experiencing low-intensity, chronic infections. Mosquito trapping and diagnostics provided strong evidence for year-round local transmission. Moreover, we present evidence that Hawaii amakihi have increased in low elevation habitats on southeastern Hawaii Island over the past decade. The recent emergent phenomenon of recovering amakihi populations at low elevations, despite extremely high prevalence of avian malaria, suggests that ecological or evolutionary processes acting on hosts or parasites have allowed this species to recolonize low-elevation habitats. A better understanding of the mechanisms allowing coexistence of hosts and parasites may ultimately lead to tools for mitigating disease impacts on wildlife and human populations.     

Apparent periapical repair without operative intervention: a case report and discussion

CASE REPORT: A case is described where substantial reduction of an established periapical lesion appeared to take place in the absence of operative intervention, and as the crown of the tooth was progressively destroyed by dental caries. The case raises debate on the pathogenesis, diagnosis and monitoring of endodontic lesions, and may stimulate renewed research interest in these most fundamental elements of clinical endodontology.     

A Case of Sacral Parasite

Abstract A case of sacral parasite is presented. A parasitic body with an incomplete lower limb was attached to the sacrococcygeal region of a female newborn at birth. The twins were easily separated by operation two days after birth. The parasite contained well developed small and/or large intestines, a multilocular cyst and a unilocular cyst. Histologically, the wall of the multilocular cyst consisted of tissues of three germ layers, such as central and peripheral nervous tissues, mature and immature intestine, pancreatic tissue, bronchial cysts, connective tissue, etc. The thick wall of the unilocular cyst consisted of central nervous tissue and connective tissue. The degree of differentiation of these tissues varied considerably. The parasite revealed no organ communication with the autosite. Since the operation, her growth and development have been favorable and no other abnormalities have been found.     

黑龙江省地方性克丁病区小学生寄生虫病情况分析

我们对黑龙江省地克病流行区397名小学生进行了寄生虫病调查。发现该区有十二种寄生虫病。肠道寄生虫病总感染率为73.3％(291/397)。口腔原虫感柒率为38.9％(35/90)。作者认为兰氏贾第鞭毛虫和口腔原虫的感染率与热带、温带、寒带无关;还认为蛔虫与蛲虫可能有拮抗作用,值得探讨。     

Association of malnutrition with amebiasis

Observation of a cohort of preschool children in Dhaka, Bangladesh, is beginning to reveal the contributions of environment, host, and parasite to amebiasis. Reviewed here are the associations and interactions of malnutrition, IgA and interferon-γ, human leukocyte antigen alleles, and parasite genotypes to the outcome of infection. Future efforts aimed at understanding the mechanisms of these effects are described.     

Evaluation of a novel kit (TF-Test) for the diagnosis of intestinal parasitic infections

Intestinal parasitic infections are currently a source of concern for Public Health agencies in developing and developed countries. Since three ovum‐and‐parasite stool examinations have been demonstrated to provide sensitive results, we designed a practical and economical kit (TF‐Test) that is now commercially available (Immunoassay Com. Ind. Ltda., São Paulo, Brazil). This kit allows the separate collection of three fecal specimens into a preservative solution. The specimens are then pooled, double‐filtered, and concentrated by a single rapid centrifugation process. The TF‐Test was evaluated in four different laboratories in a study using 1,102 outpatients and individuals living in an endemic area for enteroparasitosis. The overall sensitivity found using the TF‐Test (86.2–97.8%) was significantly higher (P<0.01) than the sensitivity of conventional techniques such as the Coprotest (NL Comércio Exterior Ltda, São Paulo, Brazil) and the combination of Lutz/Hoffman, Faust, and Rugai techniques (De Carli, Diagnóstico Laboratorial das Parasitoses Humanas. Métodos e Técnicas, 1994), which ranged from 48.3% to 75.9%. When the above combined three specimen technique was repeated with three specimens collected on different days, its sensitivity became similar (P>0.01) to that of the TF‐Test. The kappa index values of agreement for the TF‐Test were consistent (P<0.01), being higher and ranking in a better position than conventional techniques. The high sensitivity, cost/benefit ratio, and practical aspects demonstrate that the TF‐Test is suitable for individual diagnosis, epidemiological inquiries, or evaluation of chemotherapy in treated communities. J. Clin. Lab. Anal. 18:132–138, 2004. © 2004 Wiley‐Liss, Inc.     

Giardia induces proliferation and interferon gamma production by intestinal lymphocytes

BACKGROUND: Murine intraepithelial lymphocytes kill Giardia lambia; responses of human intestinal lymphocytes to this parasite are unknown. AIMS: To examine giardia induced proliferation, interferon gamma production, migration, and cytotoxicity by lymphocytes from the human intestine and peripheral blood. METHODS: Giardia were added to intraepithelial lymphocytes, lamina propria lymphocytes, and peripheral blood lymphocytes, obtained from jejunal mucosa and blood of otherwise healthy patients undergoing gastric bypass surgery for morbid obesity. Proliferation was measured by 3H-thymidine incorporation; frequency of proliferation precursors, by limiting dilution analysis; interferon gamma production, by ELISA; cytotoxicity, by 51Cr release of radiolabelled giardia and by release of serine esterases by effector lymphocytes that mediate cytotoxicity. RESULTS: The CD4+ T lymphocytes from intestine and blood proliferated in response to giardia. The stimulus by the parasite was mitogenic rather than antigenic due to the fact that the peak response was on day 3 rather than day 6, and the large number of precursors was in the range of that for mitogens. CD4+ T lymphocytes from both sites produced interferon gamma in response to giardia. Lymphocytes did not migrate towards or kill the parasite. CONCLUSIONS: Giardia induced the same degree of proliferation and interferon gamma production by CD4+ T lymphocytes in intestine and blood, but did not trigger cytotoxicity or migration.     

Trypanosoma cruzi infection induces a massive extrafollicular and follicular splenic B-cell response which is a high source of non-parasite-specific antibodies

Acute infection with Trypanosoma cruzi, the aetiological agent of Chagas’ disease, results in parasitaemia and polyclonal lymphocyte activation. It has been reported that polyclonal B‐cell activation is associated with hypergammaglobulinaemia and delayed parasite‐specific antibody response. In the present study we analysed the development of a B‐cell response within the different microenvironments of the spleen during acute T. cruzi infection. We observed massive germinal centre (GC) and extrafollicular (EF) responses at the peak of infection. However, the EF foci were evident since day 3 post‐infection (p.i.), and, early in the infection, they mainly provided IgM. The EF foci response reached its peak at 11 days p.i. and extended from the red pulp into the periarteriolar lymphatic sheath. The GCs were detected from day 8 p.i. At the peak of parasitaemia, CD138⁺ B220⁺ plasma cells in EF foci, red pulp and T‐cell zone expressed IgM and all the IgG isotypes. Instead of the substantial B‐cell response, most of the antibodies produced by splenic cells did not target the parasite, and parasite‐specific IgG isotypes could be detected in sera only after 18 days p.i. We also observed that the bone marrow of infected mice presented a strong reduction in CD138⁺ B220⁺ cells compared with that of normal mice. Hence, in acute infection with T. cruzi, the spleen appears to be the most important lymphoid organ that lodges plasma cells and the main producer of antibodies. The development of a B‐cell response during T. cruzi infection shows features that are particular to T. cruzi and other protozoan infection but different to other infections or immunization with model antigens.     

Molecular analysis of chloroquine resistance in Plasmodium falciparum in Yunnan Province, China

Resistance of Plasmodium falciparum to chloroquine (CQ) is determined by the mutation at K76T of the P. falciparum chloroquine resistance transporter (pfcrt) gene and modified by other mutations in this gene and in the P. falciparum multidrug resistance 1 (pfmdr1) gene. To determine the extent of polymorphisms in these genes in field P. falciparum isolates from Yunnan province of China, we genotyped the pfcrt codon 76, pfmdr1 codons 86 and 1246. Our results showed that although CQ has been withdrawn from treating falciparum malaria for over two decades, 90.3% of the parasites still carried the pfcrt K76T mutation. In contrast, mutations at pfmdr1 codons 86 and 1246 were rare. Sequencing analysis of the pfcrt gene in 34 parasite field isolates revealed CVIET at positions 72-76 as the major type, consistent with the theory of Southeast Asian origin of CQ resistance in the parasite. In addition, two novel pfcrt haplotypes (75D/144Y/220A and 75E/144Y/220A) were identified. Real-time polymerase chain reaction was used to determine pfmdr1 gene amplification, which is associated with mefloquine resistance. Our result indicated that in agreement with that mefloquine has not been used in this area, most (>90%) of the parasites had one pfmdr1 copy. Genotyping at two hypervariable loci showed relatively low levels of genetic diversity of the parasite population. Meanwhile, 28.4% of cases were found to contain mixed clones, which favour genetic recombination. Furthermore, despite a unique history of antimalarial drugs in Yunnan, its geographical connections with three malarious countries facilitate gene flow among parasite populations and evolution of novel drug-resistant genotypes. Therefore, continuous surveillance of drug resistance in this area is necessary for timely adjustment of local drug policies and more effective malaria control.