No abstract

Pathogenesis of myiasis due to the muscid fly Philornis decepttous in nestling pearlyeyed thrashers (Margurops fuscatus) in the Luquillo Rain Forest, Puerto Rico was investigated. Philornid larvae penetrated the host integument, underwent a period of development and growth, and established, as third instar larvae, between the dermis and the body musculature. Movement into this location plus growth and development of the fly larva appeared to be linked to the ingestion of host tissues including red blood cells, mononuclear cells which infiltrated from focal accumulations adjacent to the lesion, and necrotic cellular debris which accumulated in the lesion. The resultant increase in size of the larvae greatly displaced the host integument. Following the evacuation of the larvae for the purpose of pupation, repair of the cavernous lesion was initiated with the production of an intense organized fibrinous exudate. Macrophages and plasma cells predominated with vascular congestion in surrounding tissues. Over the 21-day nest period, nestlings were subject to successive infestations of large numbers of larvae and host responses to these appeared to signibcantly debit an energy budget responsible for nestling development and growth. Nestling mortality and post fledging survivorship appeared linked to the impact of these energy demands

In 58 sets of lungs from bighorns from western Alberta or eastern British Columbia, 91% were infected with Protostrongylus stilesi, and 38% were infected with P. rushi. Four of the five sheep free of P. stilesi were lambs. Lungs from nine near-term fetuses were negative for lungworms.All but 1 of 409 field-collected fecal samples from the same ranges contained larvae of Protostrongylus spp.; counts of larvae per gram of dry feces suggest a clumped distribution of lungworms. Analysis of monthly samples from one herd indicated a significant seasonal variation, with high numbers of larvae shed by bighorns on winter range. The use of fecal analyses in assessing severity of infection and the evolutionary significance of the clumped distribution of lungworms are discussed.

A new bioassay for chemical attractants of aquatic snails demonstrated that Biomphalaria glabrata could be attracted to or trapped in the vicinity of homogenates of lettuce. Fractionation of homogenates revealed the amino acids glutamate and proline and the primary attractants. Attraction was specific for the L form of glutamate. Proline appeared to stimulate reproductive activity. Glutathione, gamma-aminobutyric acid, and a number of other compounds had no effect. Extracts of lyophilized snail tissue also attracted other snails and may thus contain pheromones. These results permit formulation and testing of controlled-release attractants designed to overcome the repellant effects of slow-release molluscicides, as well as the design of stimulants to be used with no-release poisons.

Field data from two populations of Lampetra lamottenii (Lesueur, 1827) in Ontario, combined with informattion from experimental studies, have provided the following explanation of the transmission of Truttaedacnitis stelmioides (Vessichelli, 1910). Eggs hatch on the stream bed in spring and early summer. Newly hatched larvae are ingested by filter-feeding ammocoetes and remain in the intestine throughout the summer. After developing to the third stage, larvae migrate via the bile duct to cystic ducts of the liver where they remain in a state of arrested development for up to 4 years. During transformation of the host, third-stage larvae apparently moult at least once in the liver, reenter the intestine, and develop to maturity in transformers and adult lampreys. Eggs are released into the lamprey intestine and eventually passed from the anus. Transmission occurs mainly in early summer. Truttaedacnitis stelmioides never becomes encapsulated in the gut wall of L. lamottenii although it may in other lamprey species. Lampetra lamottenii may be the most suitable host among the lampreys. The biology of the parasite is closely linked to the metamorphosis and maturation of the lamprey. Other cucullanids may have a similar relationship with their hosts. Possibly the cucullanids are basically heteroxenous in that they use the immature stage of the host (e.g. the ammocoete) as an intermediate host.