Parasite treatment affects maternal investment in sons.

Parasitism can be a major constraint on host condition and an important selective force. Theoretical and empirical evidence shows that maternal condition affects relative investment in sons and daughters; however, the effect of parasitism on sex ratio in vertebrates is seldom considered. We demonstrate experimentally that parasitism constrains the ability of mothers to rear sons in a long-lived seabird, the European shag Phalacrocorax aristotelis. The effect contributes to the decline in offspring survival as the breeding season progresses and hence has important population-level consequences for this, and potentially other, seasonal breeders.

Severe and fatal central nervous system disease in humans caused by Baylisascaris procyonis, the common roundworm of raccoons: a review of current literature.

Baylisascaris procyonis, a parasitic infection of raccoons, causes severe neurologic disease in humans when infective eggs from raccoon feces are ingested. Definitive diagnosis is challenging, but can be made by isolation of larvae in brain biopsy or exclusion of other potential causes of eosinophilic meningoencephalitis. Prevention efforts are critical due to the lack of effective treatment.

The effect of an experimental infection of the nematode Heterakis gallinarum on hand-reared grey partridges Perdix perdix.

We compared 26 hand-reared grey partridges given an experimental infection of the caecal nematode Heterakis gallinarum with 26 uninfected ones. Under laboratory conditions after 91 days, there were no measurable clinical effects of the infection. We found no effect of treatment on the amount of food eaten or on caecal dropping production. However, treated birds, in particular females, developed slightly lower body mass (around 2%) compared to the controls. At post-mortem examination, we found a positive relationship between breast muscle mass and the number of worms collected from the caeca of treated birds. Treated birds with no worms when examined had smaller breast muscle mass (4.6%) compared to the uninfected control birds. These results are largely different to those found in a similar study that documented significant negative impacts on most of these factors in 8 infected birds compared to 6 controls. Its findings were used in a published model to support a hypothesis that H. gallinarum maintained in the environment by common pheasants, the primary host for this worm, could negatively affect wild grey partridge productivity and survival. In the same model our data would not support this hypothesis. Possible explanations for the different results from the 2 experiments are discussed. Together they suggest that only in certain, as yet unidentified circumstances, could experimental H. gallinarum infections have deleterious effects on hand-reared grey partridges.

Susceptibility of Peromyscus leucopus and Mus musculus to infection with Baylisascaris procyonis.

In this study, we compared the susceptibility of Peromyscus leucopus (white-footed mouse), a common natural intermediate host, and Mus musculus, a commonly used experimental model, to infection with larvae of the raccoon ascarid, Baylisascaris procyonis. Three groups of 10 mice of each species were given 50, 250, or 500 infective B. procyonis eggs by gavage. The mice were observed daily for clinical signs of central nervous system (CNS) disease and at necropsy the distribution of larvae in 10 body regions and organs was determined and compared. Clinical CNS disease developed in 57% of P. leucopus and 93% of M. musculus. The average clinical incubation period was significantly longer in P. leucopus (20.6 days postinfection [PI]) than in M. musculus (10.7 days PI), and clinical disease progressed slower in P. leucopus. Significantly fewer larvae were recovered from P. leucopus than from M. musculus. Most larvae were recovered from the anterior carcass and viscera of P. leucopus and from the carcass, head, and brain of M. musculus. CNS invasion was dose dependent in M. musculus but not in P. leucopus. Few or no grossly visible larval granulomas were present in P. leucopus but were abundant in M. musculus. We concluded that P. leucopus was less susceptible than M. musculus to B. procyonis infection, based on a decreased intensity of infection, longer clinical incubation period or lack of clinical disease, slower progression of disease, different larval distribution, and lower tissue reactivity to larvae.

Ocular larva migrans and histopathological lesions in mice experimentally infected with Baylisascaris transfuga embryonated eggs.

The ability of Baylisascaris transfuga larvae to cause ocular larva migrans (OLM) in mice was examined. Mice were given approximately 3500 infective eggs of B. transfuga per os. Their eyes were removed and examined either microscopically or histologically at various intervals post-infection. Larvae were recovered beginning 7 days after infection. Histologically, free larvae were observed in the posterior chamber and within the ocular membranes. Larval granulomas were present in the choroid with involvement of retinal layers. It was concluded that B. transfuga larvae have the ability to produce OLM in mice following oral infection and should be considered as possible agents of OLM in other animals and in human beings.