Angiostrongylus infections in rats and snails in northeast Thailand.

A survey of Angiostrongylus infections in rats and snails was carried out in the provinces of Ubon Ratchathani, Udon Thani. Kalasin, Chaiyaphum and Khon Kaen in northeast Thailand. Only two Rattus norvegicus (3.8%) and one Bandicota indica (1.4%) out of 151 R. rattus, 52 R. norvegicus and 69 B. indica examined were infected with adult lung worms. All worms recovered were A. cantonensis. Prevalence of infection in 423 Pila polita was 0.9% while all of 77 P. ampullacea were negative for larvae. In contrast to this 36.4% of 500 Achatina fulica harbored L3 of Angiostrongylus (with variations of between 29% and 46% in the five provinces). The average infection intensity in A. fulica was 13.6 L3 (1 to 441). Experimental infection of Wistar rats with L3 (isolated from A. fulica resulted in a recovery rate of 48.3% of adult worms of which 91.7% and 8.3% were identified as A. cantonensis and A. malaysiensis, respectively. This is the first proven finding of A. malaysiensis in northeast Thailand.

Morphology and ultrastructure of the redia and pre-emergent cercaria of Opisthorchis viverrini (Trematoda: Digenea) in the intermediate host Bithynia siamensis goniomphalus (Prosobranchia: Bithyniidae).

The intramolluscan stages of the human liver fluke Opisthorchis viverrini were investigated by light, scanning, and transmission electron microscopy. The morphology of the tegument, and the excretory system of the redia and pre-emergent cercaria as well as glandular cells, tail structure, and the eye spots of the cercarial stage are described. Possible environmental adaptations are discussed. The redia is characterized by a tegument which is folded concentrically and covered with densely arranged microvilli. This tegument is composed of a typical syncytium with submerged tegumental cells. The pre-emergent cercaria is characterized by a long tail with prominent fin folds and obliquely striated muscles. The oral sucker is well developed and protrusible, whereas the ventral sucker is faintly developed. Proteinaceous tegumental spines which are arranged transversally and different kinds of presumed sensory structures cover the cercarial body surface. Two well pigmented eye spots with rhabdomeric photoreceptors are located in the anterior part of the body. An extended protonephridial system is connected to a voluminous excretory bladder. The excretory tube opens at the end of the body and does not lead into the tail. Three types of glandular cells could be differentiated according to their vesicles, which are shed into the syncytial layer.

Morphology and ultrastructure of the digestive gland of Bithynia siamensis goniomphalus (Prosobranchia: Bithyniidae) and alterations induced by infection with the liver fluke Opisthorchis viverrini (Trematoda: Digenea).

The morphology and ultrastructure of the digestive gland of Bithynia siamensis goniomphalus and its alteration by infection with Opisthorchis viverrini were investigated by light and electron microscopy. The digestive gland of B. s. goniomphalus was composed of three different cell types: digestive cells, excretory cells, and narrow cells. In infected animals the number of excretory cells increased dramatically. Cellular injury in digestive cells as well as in excretory cells following the infection could be observed at the ultrastructural level.

Opisthorchiasis control in northeast Thailand: proposal for a new approach.

Opisthorchiasis, i.e. infection with the liver fluke Opisthorchis viverrini is an important health problem in Thailand and adjacent Laos, and its control is therefore of high priority. Pilot projects have shown that after praziquantel treatment high re-infection rates occurred within a short period of time. To reduce re-infections it is proposed to couple the time of treatment to the seasonal transmission dynamics and thus treat the population in March when risk of infection for the snail and fish intermediate and the human definitive hosts is lowest. Adjustment would save costs and time.

Studies on lophocercous cercariae from Bithynia siamensis goniomphalus (Prosobranchia: Bithyniidae).

Cercariae from Bithynia siamensis goniomphalus were studied in an area endemic for opisthorchiasis. Snails emitted different types of cercariae when shedding was induced by illumination. In addition to two lophocercous cercariae, a monostome cercaria (probably Notocotylus sp), two different furcocercariae and a xiphidiocercaria were found. Two similar types of lophocercous cercariae were distinguishable and one could be identified as Opisthorchis viverrini. To date the cercaria of O. viverrini has been regarded as the only lophocercous cercaria in the endemic area of opisthorchiasis. Therefore, differences between these cercariae were further characterized by scanning electron microscopy to enable us to avoid misinterpretations of O. viverrini in Bithynia.

Studies on metacercariae from naiads in northeast Thailand.

One hundred and eleven naiads from six different dragonfly species were investigated for the presence of metacercariae. Sixty-nine animals (62.2%) were infected with intensities up to more than 150 cysts per animal. The metacercarial cysts were characterized by light and scanning electron microscopy. Two types of metacercariae could be differentiated by morphological features of cyst surface, cyst wall and size.

Ultrastructural hepatic alterations in hamsters and jirds after experimental infection with the liver fluke Opisthorchis viverrini.

Changes in the hepatocytes of male hamsters (Mesocricetus auratus) and jirds (Meriones unguiculatus) at 220 days after experimental infection with the liver fluke Opisthorchis viverrini were studied by light and electron microscopy. The hepatocytes of the control group were characterized by an intracellular compartmentation. A globular nucleus was located centrally. The main features of the perinuclear zone were the cisternae of the rough endoplasmic reticulum (RER) and interjacent mitochondria, lysosomes, and peroxisomes. The peripheral cell region was dominated by glycogen fields and scattered lipid droplets, which were surrounded by anastomosing tubules of the smooth endoplasmic reticulum (SER). An immense proliferation of the SER was striking in the hepatocytes of animals infected with O. viverrini. Coincidentally, the intracellular compartmentation disappeared. Glycogen rosettes, RER, lysosomes, and lipid droplets were distributed irregularly all over the cell, the latter being observed more frequently than in control animals. The nuclei showed lobe-like protrusions and were enlarged. The mitochondria were often dumbbell-shaped and showed pathologic degenerations up to lysis. Our results resemble those of numerous investigations concerning hepatocellular alterations caused by N-nitroso compounds. Therefore, these observations suggest a synergistic effect for trematode infection and N-nitroso compounds in the pathogenesis of opisthorchiasis. The cellular alterations observed in the hepatocytes of Opisthorchis-infected animals together with the accumulation of intermediate filaments seen in the adjacent bile-duct epithelia and in the epithelium of the gall-bladder seem to indicate a disturbance of the cell metabolism and might be related to a neoplastic transformation.

Trichinellosis and trichinellosis control in Germany.

In nineteenth century Germany, trichinellosis was a relatively frequent disease. From 1861 to 1890 more than 12,500 cases, with an average mortality rate of 5%, were reported. As a consequence, trichinoscopy was made compulsory for the kingdom of Prussia in 1877, and a respective law was issued on June 3, 1900, for Germany as a whole. This measure led to a considerable decrease in human trichinellosis, reaching a minimum of only 49 cases for the period 1931-1940. The decrease in human cases was correlated to a constant decline of prevalence in pigs. However, after World War II, ten epidemics of human trichinellosis occurred with a total of about 2,000 cases. Sources of infection were illicitly slaughtered pigs, minced pork and sausages of partly unknown origin, and uninspected wild boars (Sus scrofa). Today, besides pigs, wild boars can be regarded as main sources of human infections. During the last two decades, two positive wild boars have been detected every year, thus demonstrating that a sylvatic cycle still exists. Measures to control trichinellosis in Germany have been limited to meat inspection. Before 1978 the only method allowed was trichinoscopy of compressed muscle samples. Then the pooled sample digestion technique and the magnetic stirrer method were introduced, which was later improved and automatized by use of the Foss Electric Trichomatic 35 and of the GMP 50 as a sampling device.

Current status of food-borne parasitic zoonoses in West Germany.

The present status of food-borne parasitic zoonoses in West Germany is characterized by a relatively high frequency of toxoplasmosis, sarcocystosis and Taenia saginata infections. From empirical data it can be estimated that 4% of the German population become infected per year by Toxoplasma gondii as well as by Sarcocystis species (S. hominis, S. suihominis). The number of T. saginata infected persons is reckoned at 900,000, which is equal to an average prevalence of 1.5%. Due to meat inspection and to modern methods of breeding and keeping pigs trichinellosis and Taenia solium infections have become rare diseases. According to eating habits there are only sporadic cases of fascioliasis and anisakiasis. Whether Diphyllobothrium latum and Opisthorchis felineus are still endemic, is unknown; it seems that the influx of refugees from areas of high endemicity never created new foci in West Germany.

[Development and regression of dermal corticosteroid atrophy. 2. Changes in compression rate]. / Untersuchungen über Entstehung und Rückbildung der dermalen Kortikosteroid-Atrophie. 2. Mitt.: Anderung der Kompressionsgeschwindigkeit.

In the 1st comm. results on development and remission of steroid-induced dermal atrophy were presented. Measurements were carried out with an instrument we constructed ourselves. This device enabled calculation of the rate of compression (CR) of a skin fold as well as determination of skin fold thickness (SFT). CR is specified in mm/log t. It is postulated that the CR depends on the viscosity of the basic substance and on the density of the collagen fiber skeletons led to an increase of SFT and CR. Loss of basic substance in quantitatively unchanged collagen skeletons led to a reduction of SFT and CR. In skin areas treated with corticosteroids, CR was reduced at roughly the same time as SFT. With the exception of hydrocortisone, the reduction was observed from about the 5th to the 10th d onwards in all products tested and became most pronounced after the 12th d. Following the end of steroid treatment (17th d), CR normalized within 6 to 10 d. It is concluded from the results that early steroid-induced dermal atrophy is caused by a lowering of the water/basic substance system. A steroid-specific inhibition of hyaluronic acid and glycosamine synthesis by the fibroblasts is assumed to be the cause of thickness loss. Skin areas treated with control ointments free of active substance displayed signs of increased hydratation.

[A pseudolymphomatous reaction in tattooing]. / Pseudolymphomatöse Reaktion in einer Tätowierung.

A pathological reaction developed in the red area of a professionally executed tattoo. The reaction appeared 12 years after tattooing. Histological examination of a biopsy specimen revealed a lymphoplasia.

[Development and regression of dermal corticosteroid atrophy. 1. Change in the skinfold thickness]. / Untersuchungen über Entstehung und Rückbildung der dermalen Kortikosteroid-Atrophie. 1. Mitt.: Anderung der Hautfaltendicke.

We developed a method to test how quickly conventional corticosteroid ointments produce a reduction of dermal thickness and how rapidly this remits. This method is based on a measurement instrument which forms a fold from a 9 mm wide area of skin and continuously compresses it. The skin fold thickness (SFT) can be calculated from the compression plot, whereas the rate of compression (CR) can be taken as a measure of the mechanical behavior of the dermis. Clobetasol-17-propionate, betamethanone-17-valerate, diflorasone-17,21-diacetate, triamcinolane acetonide, hydrocortisone (in 10% urea), hydrocortisone butyrate and a mixture of clocortolone-21-pivalate and clocortolone-21-hexynoate were tested. The steroid products were applied under occlusive conditions for 17 d (for about 10 h during the night). Apart from hydrocortisone, the steroids led to a significant reduction in skin thickness within 6 to 10 d. After the end of the 17 d test, skin thickness returned to normal within 6 to 10 d. Non-steroidal control ointments, tested in the same way, caused a slight increase in thickness of the skin.

Intestinal helminths of domestic dogs in the Hessian Neckar Valley, Federal Republic of Germany.

In a small town and its adjacent villages of the Hessian Neckar Valley, Federal Republic of Germany, 155 of the officially registered domestic dogs were examined for intestinal helminths. Twenty percent of the animals proved to be infected. The highest prevalence of 5.8% could be attributed to infections with Toxocara canis. These values are well below the average rates for dogs in the larger German cities.

Echinococcus multilocularis: identification of proteins inducing antibody formation in metacestode infection.

An approach to the identification of parasite proteins which are immunogenic in natural infections is described, using the infection with the larval stage of Echinococcus multilocularis as a parasite model. Metacestode proteins were separated by SDS-polyacrylamide gel electrophoresis, and transferred electrophoretically to nitrocellulose sheets (Western blotting). Subsequently, immune recognition of the proteins was performed with various host sera and antigen-antibody complexes were detected enzymatically. Using homologous antisera, different patterns of immunogenic bands were revealed by sera of different host species. Cross-reactions with sera from individuals infected with unrelated helminths were analysed. Four proteins of E. multilocularis which failed to show any cross-reaction were identified.

[Serological cross-reactions between Echinococcus multilocularis and Dipetalonema viteae infected rodents (author's transl)]. / Serologische Kreuzreaktionen zwischen experimentell mit Echinococcus multiocularis oder Dipetalonema viteae infizierten Nagetieren.

Sera from 30 E. multilocularis infected NMRI-mice and 30 D. viteae infected golden hamsters were tested in the indirect fluorescent antibody (IFAT) and indirect hemagglutination (IHA) tests. In the IFAT there were cross-reactions with all sera, but there were differences between the average titres. While filarial antisera gave higher titres in the homologous system (1:640 against 1:80), it was the opposite with Echinococcus antisera (1:160 against 1:640). Other differences referred to the parasite structures which fluoresced: using Echinococcus antigen the homologous sera gave a bright fluorescence of the outer protoscolex layers including the hooks, while Dipetalonema antisera showed fluorescence of the protoscolex parenchyma only. Thus it is easy to distinguish between homologous and heterologous reactions. Corresponding differences could not be found when using Dipetalonema antigen. In the IHA tests with E. granulosus antigen, which showed an average titre of 1:640 witch E. multilocularis sera, there were few cross-reactions, only 4 out of 30 Dipetalonema antisera giving a positive result.

[Experimental Echinococcus multilocularis infections of the maternal mouse and their significance for the offspring]. / Die experimentelle Echinococcus multilocularis-Infektion von Muttermäusen und ihre Bedeutung für die Nachkommen.

Experimental infection of mother mice by intraperitoneal injection of Echinococcus multilocularis cyst material does not result in the transfer of protective immunity to the offspring. In the contrary, if infected via the same route, filial mice show a lower antibody titer, when examined 36, 78 and 120 days p.i. and a higher worm burden (average: 1455 mg) in comparison with control mice born of non-infected mothers (average parasite weight: 844 mg). The question is discussed, whether these observations are due to the suppressive action of transferred antibodies or whether the offspring become immunologically tolerant by the transfer of parasite antigen.

[Intestinal helminths in Bangkok stray dogs and their role in public health (author's tranls)]. / Der Darmhelminthenbefall bei Strassenhunden in Bangkok, Thailand, und seine Bedeutung für die Gesundheit des Menschen.

Feces examination of 107 stray dogs in Bangkok, Thailand, on intestinal helminths showed the following rates: hookworms 100%, Trichuris vulpis 54.2%, Toxocara canis 6.5%, Gnathostoma spinigerum 2.8%, Spirocerca lupi 17.8%, Diphyllobothrium mansoni 1.9%, and Opisthorchis viverrini 1.9%. Out of these species hockworms (especially A. braziliense), T. canis, G. spinigerum, and D. mansoni are important sources of human cutaneous or visceral larva migrans, the latter two being special parasites of the Far East. Also O. viverrini is limited in its distribution to the Southeast Asian region; it is typical liver fluke of man in Thailand. The infection rates with these helminths show, that dogs may play a significant role as parasite reservoirs in this country.