Franz-Rainer Matuschka

Besnoitia besnoiti: Studies on the definitive host and experimental infections in cattle

Domestic cats, 11 other species of carnivorous mammals, 6 species of snakes, and whitebacked vultures were tested for their possible role as definitive hosts ofBenoitia besnoiti by feeding with cystic material from chronically infected bovines. None of the species tested is a definitive host; hence, the life cycle of this parasite remains obscure. In attempts to produce clinical cases of besnoitiosis by experimental infection, bovines were inoculated IV, SC, and IP with cystozoites or tachyzoites. Immunosuppression of the animals was essential for the development of severe cases and skin lesions; cystozoites proved to be more pathogenic than tachyzoites.

Stage-associated risk of transmission of the lyme disease spirochete by EuropeanIxodes ticks

To more closely define the risk of infection by the agent of Lyme disease in Europe, we determined whether spirochetal prevalence increases throughout the development of theIxodes ricinus vector tick. Of all ticks that could be flagged from vegetation,I. ricinus were by far the most abundant. Spirochetal infection rates in the adult stage of this tick (15%) are no higher than those in nymphs (18%) but greatly exceed those in larvae (0.7%). This tick therefore appears to attain infection mainly from the host of its larval stage, generally feeds on hosts that are noncompetent as reservoirs in its nymphal stage, and rarely inherits infection. Risk of human infection mainly derives from contact with the nymphal stage of the vector tick because the larva is rarely infected and the adult is large enough to be noticed and promptly removed.

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.

Time of repletion of subadult Ixodes ricinus ticks feeding on diverse hosts.

For a comparison of the times of day at which the subadult stages ofIxodes ricinus detach from nocturnal vs diurnal hosts, these ticks were placed on a variety of indigenous and experimental animals. The time of detachment appears to depend more on properties of the host than on the periodicity of tick behavior. Ticks on rodents, regardless of host periodicity, tended to detach late in the afternoon; those on a hedgehog detached around midnight, and those on lizards and birds, during the morning. Ticks on carnivores (dog, cat) detached throughout the daylight hours. The ability of these parasites to survive to the next developmental stage and, ultimately, to come into contact with another suitable host may be influenced by the identity of the host and, hence, by the circumstances of detachment. SubadultI. ricinus probably concentrate in the hosts nest when feeding on mammals but are scattered over the ground when feeding on lizard or avian hosts an aspect of engorgement behavior that may profoundly affect the capacity of this tick as a vector of agents of Lyme disease and other infections.

How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks

The tick Ixodes ricinus uses its mouthparts to penetrate the skin of its host and to remain attached for about a week, during which time Lyme disease spirochaetes may pass from the tick to the host. To understand how the tick achieves both tasks, penetration and attachment, with the same set of implements, we recorded the insertion events by cinematography, interpreted the mouthparts’ function by scanning electron microscopy and identified their points of articulation by confocal microscopy. Our structural dynamic observations suggest that the process of insertion and attachment occurs via a ratchet-like mechanism with two distinct stages. Initially, the two telescoping chelicerae pierce the skin and, by moving alternately, generate a toehold. Subsequently, a breaststroke-like motion, effected by simultaneous flexure and retraction of both chelicerae, pulls in the barbed hypostome. This combination of a flexible, dynamic mechanical ratchet and a static holdfast thus allows the tick to solve the problem of how to penetrate skin and also remain stuck for long periods of time.

Relative incompetence of European rabbits for Lyme disease spirochaetes

To determine whether rabbits may serve as reservoir hosts for Lyme disease spirochaetes in Europe, we compared their competence as hosts for Borrelia afzelii, one of the most prevalent European spirochaetal variants, with that of the Mongolian jird. To infect rabbits or jirds, at least 3 nymphal or adult Ixodes ricinus ticks infected with spirochaetes fed to repletion on each animal. Whereas jirds readily acquired tick-borne Lyme disease spirochaetes and subsequently infected vector ticks, rabbits exposed to tick-borne spirochaetes rarely became infectious to ticks. Only the rabbit that was infectious to ticks developed an antibody response. To the extent that I. ricinus ticks feed on European rabbits, these mammals may be zooprophylactic by diverting vector ticks from more suitable reservoir competent hosts.

Studies on the life cycle ofSarcocystis dugesii in the Madeiran wall lizardPodarcis (syn.Lacerta) dugesii

On the Madeira Islands, the recently described coccidian parasite, Sarcocystis dugesii (Matuschka and Mehlhorn 1984), appears to infect virtually all Madeiran wall lizards Podarcis (syn. Lacerta) dugesii. Preliminary laboratory efforts to complete the life cycle of this parasite in a variety of the limited range of avian and mammalian predators that exist on these islands have not succeeded. This suggests that these lizards serve as both definitive and intermediate hosts, as in the case of S. gallotiae on the Canary Islands (Matuschka and Bannert 1987). Sporocysts of this parasite are transmitted via the fecal-oral route, thereby producing another generation of sarcocysts in the lizards skeletal musculature. Cannibalized tails serve as the vehicle for transporting that stage of this parasite from one host to another, leading once again to sporocyst excretion and further cycles of transmission. Because transmission via cannibalism may not be limited to S. gallotiae, a series of laboratory experiments was carried out to determine whether Madeiran wall lizards are similarly capable of supporting the entire life cycle of S. dugesii. Tail autotomy by lizards mediates relationships with predatory animals, including those of their own species. In the course of a study on the mode of transmission of the Canarian sarcosporidian cycle, cannibalism of autotomized tails was recognized as common (Matuschka and Bannert 1987). The Madeiran wall lizard is considered to be omnivorous, mainly feeding on various arthropods as well as abundant plant matter (Sadek 1981). Tail autotomy is widespread among lizards and is generally regarded as a mechanism for escaping and surviving attacks of potential predators (Vitt and Cooper 1986). The Madeiran wall lizard rapidly