Vaccination against Lyme disease caused by diverse Borrelia burgdorferi.

Diversity and mutations in the genes for outer surface proteins (Osps) A and B of Borrelia burgdorferi sensu lato (B. burgdorferi), the spirochetal agent of Lyme disease, suggests that a monovalent OspA or OspB vaccine may not provide protection against antigenically variable naturally occurring B. burgdorferi. We now show that OspA or OspB immunizations protect mice from tick-borne infection with heterogeneous B. burgdorferi from different geographic regions. This result is in distinct contrast to in vitro killing analyses and in vivo protection studies using syringe injections of B. burgdorferi as the challenge inoculum. Evaluations of vaccine efficacy against Lyme disease and other vector-borne infections should use the natural mode of transmission and not be predicated on classification systems or assays that do not rely upon the vector to transmit infection.

[Lyme borreliosis: research gaps and research approaches. Results from an interdisciplinary expert meeting at the Robert Koch Institute]. / Lyme-Borreliose: Forschungsbedarf und Forschungsansätze. Ergebnisse eines interdisziplinären Expertentreffens am Robert Koch-Institut.

Lyme borreliosis is currently the most frequent tick-transmitted zoonosis in the northern hemisphere. Germany and other European countries are regarded as highly endemic areas; therefore the burden of disease and consequently the costs for the health systems are considered to be high. This report summarises the results of an interdisciplinary workshop on Lyme borreliosis which aimed to identify research deficits and to prioritise areas which need to be addressed. Research needs have been recognised for different areas: diagnosis, epidemiology, immunology, clinics, ecology and health services research. Examples of research areas which have priority are the standardisation of diagnostic tests, the development of markers to detect an active infection, the improvement of the epidemiological database and the analysis of the burden of disease.

Hosts on which nymphal Ixodes ricinus most abundantly feed.

To identify hosts that may serve as European reservoirs for the agent of Lyme disease, Borrelia burgdorferi, we determined whether nymphal Ixodes ricinus feed mainly on particular mice (Apodemus flavicollis or A. agrarius), voles (Clethrionomys glareolus) or on sand lizards (Lacerta agilis) and whether the abundance of these hosts corresponds to the seasonal activity of the subadult stages of the vector tick. In all sites, the mice appeared most heavily infested by larvae; at least seven parasitized each mouse, about three per vole and four per lizard. Many fewer nymphal I. ricinus parasitized A. flavicollis and C. glareolus than did larvae. Although more than 30 times as many larval than nymphal ticks parasitized the two most abundant hosts (C. glareolus and A. flavicollis), about 15 times as many fed on A. agrarius and twice as many on lizards. Nymphal and larval ticks fed on rodents at about the same time. Lizards were most abundantly parasitized by nymphs somewhat earlier than by larvae. Early in the season of transmission of Lyme disease, virtually all A. agrarius as well as lizards were potentially exposed to spirochetes borne by nymphal I. ricinus. We concluded that larval and nymphal I. ricinus differentially parasitize different hosts. Because so many of these nymphs feed on them, A. agrarius may more effectively serve as reservoirs for the agent of Lyme disease than do other putative reservoir hosts. The presence of lizards may inhibit transmission.

Diversionary role of hoofed game in the transmission of Lyme disease spirochetes.

To determine whether the presence of ungulates may inhibit transmission of the agent of Lyme disease (Borrelia burgdorferi) while promoting the abundance of its European vector tick (Ixodes ricinus), we compared the feeding density of subadult ticks on roe deer (Capreolus capreolus), red deer (Cervus elaphus), fallow deer (Dama dama), and wild sheep (Ovis ammon) near Berlin and in Brandenburg State, Germany. The prevalence of spirochetal infection in these ticks was compared with that in ticks swept from nearby vegetation. Spirochetes are present in nearly one-fifth of nonfed, questing nymphal and adult wood ticks in the region. Many ungulates in this intensely enzootic region fail to mount a detectable humoral response against the agent of Lyme disease, even when exposed to numerous infected ticks. During the height of the summer, each ungulate may support the feeding of hundreds of subadult ticks. Larvae feed lower on the bodies of hoofed game than do nymphs. Few ticks retain infection by the Lyme disease spirochete after feeding on hoofed game animals. We conclude that numerous I. ricinus ticks feed on ungulates, but that such host-contact fails to infect these ticks while eliminating pre-existing spirochetal infection.

Competence of urban rats as reservoir hosts for Lyme disease spirochetes.

To determine whether urban rats serve efficiently as reservoir hosts for the agent of Lyme disease, we recorded the frequency of infection in nymphal Ixodes ricinus (L.) ticks that had fed as larvae on experimentally infected Norway rats, Rattus norvegicus (Berkenhout), or on black rats, R. rattus (L.), and evaluated the nidicolous venue of transmission. Subadult vector ticks attached readily to Norway rats as well as black rats and virtually all became infected in the course of feeding. Larval ticks detached when these nocturnally active hosts were at rest. Rats appeared to be competent reservoir hosts of Lyme disease spirochetes in a transmission cycle in urban sites.

Subadult Ixodes ricinus (Acari: Ixodidae) on rodents in Berlin, West Germany.

To identify hosts that may serve as reservoirs for the agent of Lyme disease in Central Europe, we determined whether Ixodes ricinus L. feed most frequently on certain rodents and whether the abundance of these hosts corresponds to the season of feeding activity of the tick in four sites in Berlin, Federal Republic of Germany. In addition, we correlated abundance of I. ricinus with that of particular rodent hosts. Two small rodents were more abundant than any others; a mouse, Apodemus flavicollis, predominated in a wooded site and a vole, Clethrionomys glareolus, in three brush- or grass-covered sites. The tick was most abundant in the mouse-infested site. Although A. flavicollis comprised only about a third of rodents collected, nearly 60% of all such rodent parasitizing I. ricinus fed on this mouse. These ticks were more abundant on mice than voles in each of the study sites and throughout the year, and more larvae fed on these rodents than did nymphs. Although larval as well as nymphal I. ricinus are most abundant during midsummer, they feed on rodents from April through October. Taken together, these observations suggest A. flavicollis as a potentially important reservoir host for I. ricinus-borne infections.

Recognition of cyclic transmission of Sarcocystis stehlinii n. sp. in the Gran Canarian giant lizard.

The transmission of Sarcocystis species via cannibalism seems to be common among lizards of the genus Gallotia that are endemic to the Canary Islands. Gran Canarian giant lizards, Gallotia stehlini, were screened for the presence of sarcosporidian parasites. Sarcocysts, measuring 90-400 micrometers in length and 60-160 micrometers in width, were found in the musculature of the lizards' tails. In their feces the lizards passed sporocysts of 8.5(8.2-9.4) x 6.5(5.9-7.0) micrometers. A series of laboratory infections was carried out to shed light on the life cycle of Sarocystis stehlinii n.sp., proving it to be another dihomoxenous Sarcocystis species.

Differential detachment from resting hosts of replete larval and nymphal Ixodes ticks.

To determine whether replete subadult Ixodes ticks detach more frequently from resting than from active hosts, diverse rodents and lizards were caged in an apparatus designed to record the ticks' sites of detachment relative to the resting site of the host. Replete larval Ixodes ricinus and Ixodes dammini accumulated mainly beneath the resting places of the mice (Apodemus agrarius and Peromyscus leucopus) most frequently parasitized in nature. Although nymphal I. ricinus similarly detached where these mice rested, nymphal I. dammini detached more randomly. When lizards were used as hosts, both subadult stages of I. ricinus tended to detach away from their main resting sites; these ticks detached from squirrels more randomly. Detachment ratios for other rodent hosts, that are abundantly infested by the larvae of these ticks in nature (Apodemus flavicollis and Clethrionomys glareolus), could not be derived because nymphs generally failed to attach. Our observations are consistent with reports that both subadult stages of I. dammini, but not the adult, feed on the same kind of nest-dwelling hosts and that the host range of I. ricinus is less focused. Detachment of mouse-feeding larvae from resting mice promotes subsequent nymphal attachment to conspecific hosts, and the absence of such behavior among nymphs facilitates access of the resulting adults to deer.

Reptiles as intermediate and/or final hosts of Sarcosporidia.

A revision of the parasitic protozoan genus Sarcocystis which has reptiles as intermediate and/or final hosts is given. Twelve species described as having reptiles as intermediate hosts are considered valid species of the genus Sarcocystis. Snakes have been shown experimentally to be the final hosts of ten other Sarcocystis species which have rodents as their intermediate hosts. One species, S. podarcicolubris, has poikilothermic intermediate and final hosts. Classification of a new Sarcocystis species based either on scantily described cysts or only on sporulated oocysts or sporocysts from feces is not sufficient and cannot be justified. A new species should be recognised only after experimental retransmission and/or because of unequivocal morphological characteristics of the sarcocyst.

Infectivity of sarcocystis from donkey for horse via sporocysts from dogs.

The dog is the final host for sarcosporidia cysts from the oesophagus and diaphragm of donkeys from Sardinia. The prepatent period lasted 9 to 10 days. Sporocysts measured 12.2-13.8 X 9.2-9.9 microns. Infection of a horse with 10(5) donkey/dog sporocysts increased the rectal temperature to more than 40 degrees C on days 10 and 20 after infection. On day 138 p.i. predominantly immature cysts containing metrocytes were found, especially in the oesophagus. Infection on day 117 p.i. with 2 X 10(5) horse/dog sporocysts did not give rise to a temperature increase during the following 21 days. The final host of sarcosporidia cysts from the oesophagus and diaphragm of horses from Sardinia is the dog. The prepatent period lasted 9-10 days. Sporocysts measured 12.2-13.8 X 9.2-9.9 microns. The rise in the rectal temperature of three foals infected with horse/dog sporocysts did not differ from that of the foal infected with donkey/dog sporocysts. In both cases rectal temperature increased to more than 40 degrees C on days 10 and 20 following infection with 10(5) sporocysts. Because of the occurrence of two temperature peaks following infection, two generations of schizogony are postulated. The presence of a sarcosporidia species occurring in the donkey only is doubtful.

The effect of sulfomethoxypyrazine-pyrimethamine therapy on the fine structure of Toxoplasma gondii-cysts in the brain of Mastomys natalensis. Scanning and transmission electron microscopical investigations.

Two month old chronically infected Mastomys natalensis, which had been treated for ten days with sulfomethoxypyrazine-pyrimethamine, were utilized for testing the effect of chemotherapy on the fine structure of Toxoplasma cysts (strain ALT). After completion of the therapy, cysts were examined from the brains of killed animals in scanning and transmission electron microscopes. The scanning electron microscopic experiments revealed no or only slight morphological differences between the cysts of the untreated controls (Fig. 1) and the treated animals (Fig 2). In transmission electron microscopic studies the cyst membrane appeared less rugged (see Fig. 3,7 and the untreated control Fig. 6). The cyst basic substance often produces an optically empty space (Fig. 3,4). The pellicle of individual parasites display an unusual affinity for the pellicle of neighboring parasites (Fig. 3,5,7). In direct contrast to the untreated cysts no endodyogeny could be observed on the treated cysts examined to this point.

Endodyogeny in Isospora rastegaievae from the Eurasian hedgehog (Erinaceus europaeus L.).

Isospora rastegaievae undergoes its asexual development in the intestinal tract of hedgehogs by endodyogeny. Using light- and electron-microscopy it was demonstrated that daughter organisms were formed by typical endodyogeny as described for different coccidia.

Loss of Lyme disease spirochetes from Ixodes ricinus ticks feeding on European blackbirds.

To determine whether blackbirds (Turdus merula), the most abundant and most abundantly tick-infested ecotonal bird of Central Europe, may contribute to the transmission of the Lyme disease spirochete (Borrelia burgdorferi), we compared the infectivity to ticks of naturally as well as experimentally infected blackbirds and rodents. European blackbirds experience intense exposure to Ixodes ricinus ticks and to the pathogens that they transmit. In nature, subadult I. ricinus ticks found feeding on these birds generally contain no spirochetes, although infection is universal in those found on black-striped mice (Apodemus agrarius). Those found on yellow-necked mice (A. flavicollis) are less frequently infected. Ticks lose infection in the course of feeding on blackbirds and fail to infect them. Subadult I. ricinus ticks readily feed on blackbirds, black-striped mice, and jirds (Meriones unguiculatus), but engorge less fully on the bird than on the rodents. Although birds may burden human health by establishing new infestations of I. ricinus ticks, our observations indicate that particular birds may benefit health by locally diminishing transmission of the Lyme disease spirochete.

Cannibalism and autotomy as predator-prey relationship for monoxenous Sarcosporidia.

In search for the final host of Sarcocystis gallotiae, sarcocysts of naturally infected Canarian lizards, Gallotia galloti, were fed to vertebrate predators of the lizard. Repeated transmission experiments remained negative. Routine check of the feces of the wild G. galloti revealed shedding of sporocysts. The sporocysts were administered to small vertebrates, which may function as prey for G. galloti. The transmission experiments remained negative. The observation of a high intraspecific aggression of G. galloti, including cannibalism and autotomy, seemed to support the hypothesis that this behavior might be the base of a an unexpected predator-prey relationship. Sarcocysts of S. gallotiae, fed to two laboratory-bred G. galloti resulted in excretion of sporulated sporocysts measuring 9.7 (9.2-12.2) X 7.7 (6.6-9.2) microns. Oral inoculation of two laboratory-bred G. galloti with experimentally gained sporocysts, led to the development of sarcocysts of 150-200 microns in length and 80-110 microns in width in the musculature of the lizards 153 days p.i. The sarcocysts were identified as S. gallotiae by light and electron microscopy. In epithelial cells of the intestine of G. galloti, which had experimentally been infected with sarcocysts of S. gallotiae, stages of gamogony and sporogony were found. We suggest that the life cycle of S. gallotiae is monoxenous and not obligatorily heteroxenous. The genus Sarcocystis seems to be more flexible in its biologic adaptability to utilize autotomy and cannibalism for completing its cycle than had heretofore been assumed.

[The development of weaned piglets experimentally infected with Isospora suis as a model for the effect of lasalocid and halofuginone on coccidia (author's transl)]. / Die Entwicklung experimentell mit Isospora suis infizierter Absatzferkel als Modellfall für die Wirksamkeit von Lasalocid und Halofuginon auf Kokzidien.

Piglets which were early-weaned at the age of 21.7 days and experimentally monoinfected with oocysts of Isospora suis showed distinct reductions in zootechnical criteria during an experimental period of 4 weeks. The daily liveweight gains in the infected piglets (group B) was 19.7% lower than in the control group A, which was free of Coccidia. Comparative photographs with the REM showed serious lesions in the small intestine of infected piglets, which are thought to be mainly responsible for the reduced productivity. The application of 150 mg Lasalocid per kg of total feed to infected piglets caused the rate of weight gain to attain the same values as the noninfected controls (group A). Piglets receiving Lasalocid treatment passed oocysts with the faeces which were infectious. On the other hand, infected piglets which were treated with 6 mg Halofuginone per kg of total feed did not contain any oocysts in the faeces. Despite having a higher liveweight at the beginning of the experiment, this group only gained as much liveweight as the infected piglets (group B). This depression in liveweight gains could be explained by the significantly reduced uptake of feed, which was 21.1% lower than in the controls (group A). 6 weeks after the first infection, a re-infection resulted in the appearance of oocysts in the faeces of the piglets which had been treated with Halofuginone. On the other hand, the animals treated with Lasalocid had developed an efficient immunity to Isospora suis.

[On micromorphological changes of bradyzoites of toxoplasma cysts in cerebral tissue after storage under freezing at--20 degrees C (author's transl)]. / Uber mikromorphologische Veränderungen an Bradyzoiten von Toxoplasma-Zysten im Hirngewebe nach Tiefgefrieren bei--20 degrees C.

Toxoplasma bradyzoites in cerebral tissue are no longer infectious and able to replicate after 24 hrs of storage under freezing at--20 degrees C. No intact bradyzoites could micromorphologically be demonstrated in the cysts. Clear changes in the structure and lesions of the cell walls and basic substance of the cysts, and of the bradyzoites are held responsible for the destruction of the parasites being surrounded by host tissue.

[Final host specificity of sarcocystis species transmitted by dogs (authors's transl)]. / Zur Endwirtspezifität der vom Hund übertragenen Sarkosporidienarten.

Dogs and raccoons were fed muscle of various intermediate hosts that had been infected either naturally or artificially wit Sarcocystis species transmitted from dogs. The muscle samples used for the experiments contained cysts of the following species: S. sp. of the donkey, S. bovicanis of cattle, S. ovicanis and S. sp. of sheep, S. suicanis of pigs, or S. capracanis and S. sp. of goats. In all trails, the dogs shed sporocysts of the Sarcocystis species concerned after a typical prepatency. In the faeces of the raccoons sporocysts were only found after they were fed on porcine muscle containing S. suicanis. The prepatency in raccoons was 9 days. Both the prepatent period of S. suicanis and the size of the excreted sporocysts were identical in dogs and raccoons. Sporocysts isolated from raccoon faeces were infective for pigs. Thus the raccoon was established as an additional final host of S. suicanis, and may be of significance in the epidemiology of this parasite in the European wild boar.

The emergence of Lyme disease in a changing environment in North America and central Europe.

Lyme disease has recently begun to emerge as a significant threat to human health, both in Europe and the United States. Late sequellae, resembling those of neurosyphilis and multiple sclerosis, may occur many years after initial infection. Spontaneous abortion accompanies arthritis, carditis and neuritis as burdensome short-term sequellae. Thousands of new infections are recognized each year on each side of the Atlantic, although reporting may be incomplete. The disease was described in Europe nearly a century ago and named erythema chronicum migrans, but its etiology has only recently been defined. The name "Lyme disease" was coined to describe a particularly intense American focus of disease, but the term has gained wide acceptance on both continents. The identity of the American and European etiological agents involved has yet to be determined. In America, a deer-associated, often bird-transported tick transmits this mouse-reservoired spirochete. The European situation seems more complex because the vector tick feeds on a greater variety of vertebrates. The reservoir hosts of the spirochete have yet to be determined. The role of Ixodes ricinus and possible other vectors in perpetuating transmission of the European infection remains to be defined. Whether I. ricinus as well as I. dammini merely serve as a bridge to the human population or are important for the maintenance of the feral cycle remains to be seen. The capacity of a tick to maintain transmission of Lyme disease spirochetes depends upon a complex set of properties, including competence as a host for the spirochete, a pattern of feeding that focuses on a particular reservoir favored by a pattern of tick activity, during each transmission season, in which nymphs feed before larvae. Transmission would be favored by an environment, such as that of islands, in which the variety of potential reservoir hosts is restricted. Hosts, for example reptiles, that might fail to support growth of the spirochete would serve to dilute effective transmission in nature. Similarly, the capacity of a vertebrate to maintain the infection requires long-term support of the spirochete in a tissue site accessible to vector ticks, tolerance of repeated feeding by vector ticks and a pattern of host activity that exposes the host to numerous bites. The intensity of infection depends upon a continuous pattern of transmission in which each generation is infected anew. The rare event in which the vector inherits infection would serve mainly to transport the spirochete to a new site, most effectively by migrating birds.(ABSTRACT TRUNCATED AT 400 WORDS)

Mating strategies and spermiogenesis in ixodid ticks.

Mate-seeking and sperm-transfer in the ixodid hard ticks, which include important vectors of zoonotic pathogens, generally reflect their peculiarly prolonged pattern of feeding. The metastriate ticks, including Dermacentor, Amblyomma, and Rhipicephalus, invariably attain sexual maturity and mate solely on their hosts. The more primitive prostriate Ixodes ticks, however, may copulate both in the absence of hosts and while the female engorges. These expanded opportunities for insemination complicate the mating systems of the Ixodes ricinus complex of species. In these ticks, autogenous spermatogenesis must precede host contact, whereas anautogenous oogenesis requires that the females store sperm. All hard tick males undergo a courting ritual before they can deposit their spermatophores within the female's genital tract. These diverse and prolonged patterns of sexual interaction provide opportunities for interactions between populations and individuals that may be relevant to the role of ticks as vectors of zoonotic pathogens.