Seasonal variation in the prevalence and intensity of canine Gnathostoma spinigerum infection in northeastern Thailand

Canine Gastric Pathology: A Review

Gastric disorders are common in dogs and are a major reason for veterinary consultation. In human medicine, the classification of gastric diseases based on histological features, genotypes and molecular phenotypes helps to better understand the characteristics of each subtype, and to improve early diagnosis, prevention and treatment. Canine gastric lesions often show strong histological similarities to their human counterparts. However, such conditions in the canine stomach are poorly studied and their cellular and molecular features are largely unknown. This article reviews the histopathological classification of inflammatory and neoplastic lesions of the canine stomach and provides an update on the application of molecular techniques within the field of canine gastric pathology. The canine disorders are compared with current knowledge of the equivalent human diseases.

Spontaneous cure after natural infection with Gnathostoma turgidum (Nematoda) in Virginia opossums (Didelphis virginiana)

Seasonality of the nematode Gnathostoma turgidum in Virginia opossums (Didelphis virginiana) in the wild has been reported; however, the mechanisms involved in deworming are unknown. We monitored the parasitologic and biologic changes in four Virginia opossums naturally infected with G. turgidum by coproparasitologic examination and abdominal ultrasonography. Eggs became detectable in the feces of opossums in May, peaked in July and August, and suddenly decreased in October. Adults of G. turgidum were expelled in the feces mainly in September. Ultrasonography of the liver showed slight damage during May. Lesions in the stomach appeared in April and persisted until September. The abnormalities of the liver and stomach were resolved in November. These data suggest that G. turgidum is likely expelled as a result of host immunologic mechanisms, although termination of a natural life span cannot be definitively excluded.

Helminth infections of the central nervous system occurring in Southeast Asia and the Far East

Although helminth infections of the central nervous system (CNS) are rare, their public health implications must not be neglected. Indeed, several helminth species can cause cerebrospinal infections, especially if humans serve as intermediate or non-permissive host. The diagnosis of cerebrospinal helminthiases is difficult, and the detection of parasites in cerebrospinal fluid is rarely successful. Cerebrospinal helminth infections therefore often remain undetected, and hence prognosis is poor. Increases in tourism and population movements are risk factors for cerebrospinal helminthiases and infections pose particular challenges to clinicians in non-endemic areas. In this review, we focus primarily on food-borne helminthiases that are endemic and often emerging in Southeast Asia and the Far East, namely angiostrongyliasis, gnathostomiasis, sparganosis, paragonimiasis and cysticercosis. Additionally, we discuss neuroschistosomiasis, a disease that is transmitted through human-water contact. For each disease, we describe the pathogen, its transmission route and possible mechanisms for entering the CNS. We also summarise common signs and symptoms, challenges and opportunities for diagnosis, treatment, clinical management, geographical distribution and epidemiology. The adoption of a comprehensive set of diagnostic criteria for different cerebrospinal helminthiases is proposed, including epidemiological history, typical signs and symptoms, neuroimaging and laboratory findings. Finally, risk factors, and research needs for enhanced patient management and population-based control measures are discussed.

Is Gnathostoma turgidum an annual parasite of opossums? Drastic seasonal changes of infection in Didelphis virginiana in Mexico

Gnathostoma turgidum is a nematode that parasitizes the stomach of opossums, Didelphis virginiana. Despite its wide distribution in the Americas, its natural life cycle is poorly understood. Recently, we found an endemic area for G. turgidum infection in Sinaloa, Mexico (Diaz-Camacho et al., 2009). Based on sporadic surveys for several years, the prevalence was apparently high in summer and extremely low in winter. To confirm that this is really a seasonal variance, we conducted a longitudinal survey on G. turgidum infection in opossums from November 2007 to November 2008. The results showed amazing seasonal changes in the prevalence, with synchronized migration and maturation of worms in opossums. Between February and March, many juvenile worms, with occasional AL3, were found in the liver, but no worms were found in the stomach. Mature adult worms began to appear in the stomach around April and rapidly increased in number toward July, when all worms resided in the stomach. Then, the worms disappeared almost completely by November. These results suggest that G. turgidum is an annual parasite of the opossum, D. virginiana, in Mexico.

Waterborne zoonotic helminthiases

This review deals with waterborne zoonotic helminths, many of which are opportunistic parasites spreading directly from animals to man or man to animals through water that is either ingested or that contains forms capable of skin penetration. Disease severity ranges from being rapidly fatal to low-grade chronic infections that may be asymptomatic for many years. The most significant zoonotic waterborne helminthic diseases are either snail-mediated, copepod-mediated or transmitted by faecal-contaminated water. Snail-mediated helminthiases described here are caused by digenetic trematodes that undergo complex life cycles involving various species of aquatic snails. These diseases include schistosomiasis, cercarial dermatitis, fascioliasis and fasciolopsiasis. The primary copepod-mediated helminthiases are sparganosis, gnathostomiasis and dracunculiasis, and the major faecal-contaminated water helminthiases are cysticercosis, hydatid disease and larva migrans. Generally, only parasites whose infective stages can be transmitted directly by water are discussed in this article. Although many do not require a water environment in which to complete their life cycle, their infective stages can certainly be distributed and acquired directly through water. Transmission via the external environment is necessary for many helminth parasites, with water and faecal contamination being important considerations. Human behaviour, particularly poor hygiene, is a major factor in the re-emergence, and spread of parasitic infections. Also important in assessing the risk of infection by water transmission are human habits and population density, the prevalence of infection in them and in alternate animal hosts, methods of treating sewage and drinking water, and climate. Disease prevention methods, including disease surveillance, education and improved drinking water treatment are described.

Cutaneous larva migrans, sacroileitis, and optic neuritis caused by an unidentified organism acquired in Thailand

We report the case of a 32-year-old pregnant woman with an unidentified intraocular parasite. The parasite, which had been acquired in Thailand, caused cutaneous larva migrans, sacroileitis, and 2 years later optic neuritis and panuveitis. The patient was successfully treated with ivermectin and albendazole. The diagnostic possibilities of this peculiar presentation are discussed. Parasitic infections are a leading cause of medical problems in travelers to tropical countries.1 While most parasites cause gastrointestinal problems, some may migrate throughout the body and lodge in critical organs. Ocular parasitic infections may occur by direct inoculation onto the eye,2 or incidentally during systemic migration. Subconjunctival parasites are easily diagnosed by removal and careful microscopic examination.3 Parasites, which lodge within the eye, are more difficult to diagnose, especially if not removed. In this report we describe a patient who presented with an intraocular parasite causing optic neuritis and panuveitis, 2 years after travel to Thailand.