Eosinophilic meningitis due to Angiostrongylus and Gnathostoma species.

Eosinophilic meningitis can be the result of noninfectious causes and infectious agents. Among the infectious agents, Angiostrongylus cantonensis and Gnathostoma spinigerum are the most common. Although angiostrongyliasis and gnathostomiasis are not common in the United States, international travel and immigration make these diseases clinically relevant. Both A. cantonensis and G. spinigerum infection can present as severe CNS compromise. Diagnoses of both infections can be challenging and are often clinical because of a paucity of serological assays readily available in the United States. Furthermore, there are conflicting recommendations about treatment for angiostrongyliasis and gnathostomiasis. To further explore the emerging nature of these helminthic infections, a case description and review of A. cantonensis and G. spinigerum infections are presented. The clinical severity of eosinophilic meningitis and diagnosis of these infections are highlighted.

Toxoplasma gondii and Toxocara spp. co-infection.

Toxoplasma gondii and Toxocara spp. infections can cause systemic and ocular disease. To estimate the prevalence of infection with these organisms, we tested serum samples from persons > or = 12 years of age obtained in the Third National Health and Nutrition Examination Survey (1988-1994). Among those tested for both T. gondii and Toxocara spp. (n = 16,646), the age-adjusted T. gondii antibody prevalence was 23.6% (95% confidence limit [CL] = 22.1-25.1%) and the Toxocara spp. antibody prevalence was 14.0% (95% CL = 12.7-15.4%). Multivariate analysis controlling demographic and risk factors showed that persons infected with Toxocara spp. were more likely to be infected with T. gondii (odds ratio [OR] = 1.93, 95% CL = 1.61-2.31), and similarly, persons infected with T. gondii were more likely to be infected with Toxocara spp. (OR = 1.91, 95% CL = 1.59-2.28). Infection with T. gondii and Toxocara spp. are common and can be prevented by many similar interventions.

Prevention and control of cystic echinococcosis.

Human cystic echinococcosis (hydatid disease) continues to be a substantial cause of morbidity and mortality in many parts of the world. Elimination is difficult to obtain and it is estimated that, using current control options, achieving such a goal will take around 20 years of sustained efforts. Since the introduction of current (and past) hydatid control campaigns, there have been clear technological improvements made in the diagnosis and treatment of human and animal cystic echinococcosis, the diagnosis of canine echinococcosis, and the genetic characterisation of strains and vaccination against Echinococcus granulosus in animals. Incorporation of these new measures could increase the efficiency of hydatid control programmes, potentially reducing the time required to achieve effective prevention of disease transmission to as little as 5-10 years.

Impact of overgrazing on the transmission of Echinococcus multilocularis in Tibetan pastoral communities of Sichuan Province, China.

BACKGROUND: Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities. METHODS: Grazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression. RESULTS: In the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open (common) pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced (private) pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection (P = 0.003, OR = 1.048). CONCLUSION: Overgrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals.

Socioeconomic and behavior risk factors of human alveolar echinococcosis in Tibetan communities in Sichuan, People's Republic of China.

Data from two cross-sectional investigations on 7,138 subjects were used to explore risk factors of human alveolar echinococcosis (AE) in Tibetan communities. The overall human AE prevalence was 3.1% (223 of 7,138), females had a higher prevalence (3.6%, 132 of 3,713) than males (2.7%, 91 of 3,425; P = 0.011), and herdsmen had a higher prevalence (5.2%, 154 of 2,955) than farmers (1.8%, 12 of 661; P < 0.001) and urban populations (2.1%, 49 of 2,360; P < 0.001). Age in all populations, number of dogs kept, fox skin ownership in farmers, not preventing flies from landing on food in herdsmen, using open streams as drinking water sources, and playing with dogs in urban populations were statistically significant risk factors. The results suggest that AE is highly endemic in the eastern Tibetan plateau, in Sichuan Province, the role of the dog is important for human infection, and other factors associated with environmental contamination may vary according to structure and practices of communities.

Progress in diagnosis, treatment and elimination of echinococcosis and cysticercosis.

Here I review the current status of geographical occurrence and public health significance of echinococcosis (Echinococcus spp. infections) and cysticercosis (Taenia solium infection) with special emphasis on the remarkable technologic progress achieved in recent decades that has led to greater understanding of the biology and epidemiology of these cestode infections. The greatest remaining challenges are to apply this knowledge and technology to improved medical management and prevention of these infections.

Cystic echinococcosis in the Americas.

Echinococcus granulosus and related genotypic variants, the agents of cystic hydatid disease, occur widely in the American continents from Alaska and Northern Canada in North America to Tierra del Fuego in South America. Here we review the historical and current distribution and prevalence of these infections throughout the American countries and the results of programs to control or eliminate the infection.

Usefulness of severe combined immunodeficiency (scid) and inbred mice for studies of cysticercosis and echinococcosis.

The topics in this review are the usefulness of immunodeficient and inbred mice for studies of developmental biology, drug efficacy and host specificity in cysticercosis and echinococcosis. In non-obese diabetic severe combined immunodeficiency (NOD/Shi-scid) mice of both sexes, in vitro hatched oncospheres of all three human taeniid species (Taenia solium, Taenia saginata and Taenia asiatica) developed into cysticerci comparable to or bigger than those developed in their known intermediate host animals, whereas only females were susceptible to these infections in other scid mice of BALB/c, C57BL or C.B-17 inbred strains. Detailed morphological observation from post-oncospheral to cysticercus developmental stages is expected to be easy when we use NOD/Shi-scid mice experimentally inoculated with in vitro hatched oncospheres. Metacestocidal effect of oxfendazole was evaluated in NOD/Shi-scid mice experimentally inoculated with oncospheres of T. solium. In Echinococcus multilocularis infection, larval tissue proliferated without induction of inflammatory host responses in scid mice, thus facilitating isolation of the larval vesicles and protoscoleces for biochemical and molecular biological studies. Trans portal inoculation of metacestode tissues resulted in proliferation of secondary echinococcal foci localized exclusively in the liver without metastasis to other tissues or organs. The advantages of a mouse model for Echinococcus granulosus are also described.

Echinococcus shiquicus, a new species from the Qinghai-Tibet plateau region of China: discovery and epidemiological implications.

In Shiqu County of the Qinghai-Tibet plateau, many wild and domestic mammals are involved in the transmission cycles of Echinococcus spp. Echinococcus multilocularis and Echinococcus granulosus genotype G1 (sheep strain) are sympatrically distributed in the plateau. In 1995, we identified a unique strobilate stage of Echinococcus from the Tibetan fox, Vulpes ferrilata, but considered it to be a variant of E. multilocularis. Subsequent molecular genetic studies revealed that a hydatid cyst from the plateau pika, Ochotona curzoniae, had unique mitochondrial DNA sequences which are dissimilar to any published sequences of Echinococcus. The same sequences were subsequently found in adult worms from Tibetan foxes. Morphological, genetic and ecological features of the cestode led us to designate a new species Echinococcus shiquicus. E. shiquicus has been found at other areas surveyed on the plateau; however, no infections in humans caused by E. shiquicus have been yet identified.

Prevalence and risk factors for Giardia and coccidia species of pet cats in 2003-2004.

Prevalence and risk factors for feline coccidia and Giardia species infections were estimated for cats visiting 434 Banfield hospitals in 40 states in 2003-2004. Evaluated were 631,021 cats making 1,456,712 office visits (encounters) and having 211,105 fecal examinations. The overall fecal prevalences of coccidia and Giardia species were 1.4% and 0.58%, respectively. Cats at increased risk of coccidia infection were under 4 years of age, intact, and seen during the summer, fall, and spring months compared to winter. Cats at increased risk of Giardia species infection were under 4 years of age. Those at decreased risk were mixed breed and seen during the summer, fall, and spring. The highest regional risk of coccidia and Giardia species infection was for cats in the East South Central region and Mountain region, respectively, compared to the South Pacific region.

Estimated prevalence of nematode parasitism among pet cats in the United States.

OBJECTIVE: To estimate prevalences of roundworm, hookworm, and whipworm infections in pet cats in the United States and identify risk factors for parasitism. DESIGN: Retrospective period prevalence survey. STUDY POPULATION: 356,086 cats examined at 359 private veterinary hospitals during 2003. PROCEDURE: Electronic medical records were searched to identify cats for which fecal flotation tests had been performed and to determine proportions of test results positive for roundworms, hookworms, and whipworms. Potential risk factors for roundworm and hookworm infection were identified by means of multivariate logistic regression analysis. RESULTS: A total of 80,278 tests were performed on fecal samples from 66,819 cats. Calculated prevalences of roundworm, hookworm, and whipworm infection were 2.92%, 0.63%, and 0.031%, respectively. Age, reproductive status, breed, and season were significant risk factors for roundworm infection, with cats < 4 years old; sexually intact cats; mixed-breed cats; and cats examined during the summer, fall, or winter more likely to be infected. Age, reproductive status, and season were significant risk factors for hookworm infection, with cats < 1 year old, sexually intact cats, and cats examined during the summer more likely to be infected. Regional differences in prevalences of roundworm and hookworm infection were found. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that prevalences of nematode infections among pet cats in the United States may be lower than previously suspected on the basis of prevalences reported among cats in humane shelters and those reported in more geographically focused studies.

Echinococcus shiquicus n. sp., a taeniid cestode from Tibetan fox and plateau pika in China.

The taeniid cestode Echinococcus shiquicus n. sp. was found from the Tibetan fox Vulpes ferrilata and the plateau pika Ochotona curzoniae in the Qinghai-Tibet plateau region of China. In the adult stage, E. shiquicus from the foxes is morphologically similar to Echinococcus multilocularis. However, the new species is differentiated by its smaller rostellar hooks, fewer segments, distinct position of genital pore in the mature segment and fewer eggs in the gravid segment. Hydatid cysts of E. shiquicus found in the livers from the pikas were essentially unilocular but an oligovesicular cyst was also found. The data of mitochondrial and nuclear DNA sequences proved E. shiquicus to be a valid taxon.

Epidemiology of neurocysticercosis in Houston, Texas.

We identified 114 patients with neurocysticercosis admitted to Ben Taub General Hospital in Houston, Texas between January 1994 and June 1997. Most of these patients were born in Mexico (78%) or Central America (16%), but 6% were born in the United States. Review of neurology clinic records identified 54 patients diagnosed with neurocysticercosis, representing 2% of all neurology clinic patients and 16% of all Hispanics diagnosed with seizures. Forty-one patients were interviewed and all reported significant risk factors for infection, including ingestion of undercooked pork, pig husbandry, immigration from and frequent travel to villages in disease-endemic areas, or personal/family history of taeniasis. Among Mexican immigrants, most were born in rural areas in Central (31%) or north central Mexico (38%). Significantly fewer of the patients were from the border states (15%). The median period from immigration to diagnosis was 58 months, but it was 28 months for the 13 patients who had not left the United States after immigration. Although neurocysticercosis is being diagnosed with increasing frequency in the United States, acquisition of infection is still strongly associated with pig husbandry in rural Latin America, with little evidence of local transmission. Even among urban immigrants to the United States and United States-born cases, there is close ongoing contact with disease-endemic villages.

Two atypical cases of cystic echinococcosis (Echinococcus granulosus) in Alaska, 1999.

Before 1999, clinical experience demonstrated that the sylvatic (or Northern) biotype of Echinococcus granulosus seen in Alaska produced fewer complications and serious sequelae than infection with the pastoral (or European) biotype found in other parts of the world. Two cases of E. granulosus with severe sequelae occurred in Alaska in 1999. The adverse outcomes could have been rare complications that are part of the clinical spectrum of disease caused by sylvatic cystic echinococcus, an indication that the sylvatic biotype, especially when affecting the liver, has potential for severe clinical consequences, or perhaps in one case, infection with a more virulent biotype of E. granulosus contracted during visits to Washington State.

Short report: Identification of Echinococcus species from a yak in the Qinghai-Tibet plateau region of China.

The species identification of an echinococcal lesion in the liver of a yak in the Qinghai-Tibet plateau region of China, where both Echinococcus granulosus and E. multilocularis are present, was difficult to determine because of the atypical appearance of the lesion. Polymerase chain reaction-based mitochondrial genotyping allowed us to discriminate the Echinococcus species. Nucleotide sequences of the cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) genes amplified from the echinococcal lesion demonstrated that the yak was infected with the E. granulosus G1 genotype (sheep strain).

The US Centers for Disease Control and Prevention (CDC) and research and control of cysticercosis.

It is generally recognized that it is not possible to adequately protect the health of any nation without addressing infectious disease problems that occur elsewhere in the world. In 2002, the US Centers For Disease Control and Prevention (CDC) developed a revised strategy for consolidating, enhancing, and improving the effectiveness of CDC's efforts to prevent and control infectious diseases on a global scale. Taenia solium is one example of an imported infection disease, which impacts on the health of the US population but requires international coordinated efforts to prevent or limit transmission. This report outlines CDC's refocused global infectious disease strategy and how CDC collaborates in international efforts to eliminate taeniasis/cysticercosis.

Fenced pasture: a possible risk factor for human alveolar echinococcosis in Tibetan pastoralist communities of Sichuan, China.

Alveolar echinococcosis, infection caused by the parasitic helminth Echinococcus multilocularis, is a zoonosis strongly linked to climatic and ecological factors. Cross-sectional survey data were used to test a hypothesis that partial fencing of pastures could promote alveolar echinococcosis transmission in semi-nomadic pastoral communities of the Tibetan plateau, PR China. Using multiple stepwise logistic regression with consideration of factors of age and gender, it was shown that partial fencing around the settlements in winter pasture was significantly and independently associated with the risk of human alveolar echinococcosis in the surveyed villages (P = 0.021). The underlying reason may lie in overgrazing, an assumed cause of population outbreaks of small mammal intermediate hosts of the parasite on the Tibetan plateau. Overgrazing may have been exacerbated by the reduction of communal pastures nearby the settlements due to introduction of partial fencing around group tenure pastures acquired by Tibetan pastoralist families.

Control of echinococcosis and cysticercosis: a public health challenge to international cooperation in China.

Echinococcosis, both cystic and alveolar, and Taenia solium cysticercosis are the most serious zoonotic cestodoses worldwide. Because of the emerging importance of these diseases in China, several international workshops and meetings were held in this country from 1998 to 2001. Based on round table discussions in Chengdu 2000, the proposal of a strategy to control echinococcosis and cysticercosis has been prepared in China. It includes a comprehensive approach based on a careful analysis of the local situations (particularly concerning the particularities of the cycle, ecology, and ethology of the animal hosts, and behavioral characteristics of the population at risk), the use of newly developed tools both in animals and human (immunology, molecular biology, and imaging), and the association of the traditional control measures (control of slaughtering, antiparasitic treatment and control of the definitive hosts, and health education) with more recent developments such as vaccination of the intermediate hosts. Plans on for the control of echinococcosis and cysticercosis in China are summarized.

Economic impact of cystic echinococcosis in peru.

BACKGROUND: Cystic echinococcosis (CE) constitutes an important public health problem in Peru. However, no studies have attempted to estimate the monetary and non-monetary impact of CE in Peruvian society. METHODS: We used official and published sources of epidemiological and economic information to estimate direct and indirect costs associated with livestock production losses and human disease in addition to surgical CE-associated disability adjusted life years (DALYs) lost. FINDINGS: The total estimated cost of human CE in Peru was U.S.$2,420,348 (95% CI:1,118,384-4,812,722) per year. Total estimated livestock-associated costs due to CE ranged from U.S.$196,681 (95% CI:141,641-251,629) if only direct losses (i.e., cattle and sheep liver destruction) were taken into consideration to U.S.$3,846,754 (95% CI:2,676,181-4,911,383) if additional production losses (liver condemnation, decreased carcass weight, wool losses, decreased milk production) were accounted for. An estimated 1,139 (95% CI: 861-1,489) DALYs were also lost due to surgical cases of CE. CONCLUSIONS: This preliminary and conservative assessment of the socio-economic impact of CE on Peru, which is based largely on official sources of information, very likely underestimates the true extent of the problem. Nevertheless, these estimates illustrate the negative economic impact of CE in Peru.