Vector salivation and parasite transmission

Saliva of blood-sucking arthropods contains substances that counteract the host's hemostatic and inflammatory reactions, allowing the arthropod to locate blood and keep it flowing during the blood meal. Parasites may manipulate this system in order to achieve increased transmission, both to vertebrate and to invertebrate hosts. Additionally, salivary pharmacological substances may locally immunosupress the delivery site, allowing initial colonization of the vertebrate host by the parasite.

Epidemiological traits of the malaria-like parasite Polychromophilus murinus in the Daubenton¿s bat Myotis daubentonii.

BackgroundThe great diversity of bat haemosporidians is being uncovered with the help of molecular tools. Yet most of these studies provide only snapshots in time of the parasites discovered. Polychromophilus murinus, a malaria-like blood parasite, specialised on temperate-zone bats is a species that is being `rediscovered¿. This study describes the infection dynamics over time and between host sex and age classes.MethodsFor three years we followed the members of three breeding colonies of Myotis daubentonii in Western Switzerland and screened them for the prevalence and parasitemia of P. murinus using both molecular tools and traditional microscopy. In order to identify more susceptible classes of hosts, we measured, sexed and aged all individuals. During one year, we additionally measured body temperature and haematocrit values.ResultsJuvenile bats demonstrated much higher parasitemia than any other age class sampled, suggesting that first exposure to the parasite is very early in life during which infections are also at their most intense. Moreover, in subadults there was a clear negative correlation between body condition and intensity of infection, whereas a weak positive correlation was observed in adults. Neither body temperature, nor haematocrit, two proxies used for pathology, could be linked to intensities of infection.ConclusionIf both weaker condition and younger age are associated with higher infection intensity, then the highest selection pressure exerted by P. murinus should be at the juvenile stage. Confusion over the identities and nomenclature of malarial-like parasites requires that molecular barcodes are coupled to accurate morphological descriptions.

Female plumage spottiness and parasite resistance in the barn owl (Tyto alba)

The hypothesis that extravagant ornaments signal parasite resistance has received support in several species for ornamented males but more rarely for ornamented females. However, recent theories have proposed that females should often be under sexual selection, and therefore females may signal the heritable capacity to resist parasites. We investigated this hypothesis in the socially monogamous barn owl, Tyto alba, in which females exhibit on average more and larger black spots on the plumage than males, and in which males were suggested to choose a mate with respect to female plumage spottiness. We hypothesized that the proportion of the plumage surface covered by black spots signals parasite resistance. In line with this hypothesis, we found that the ectoparasitic fly, Carnus hemapterus, was less abundant on young raised by more heavily spotted females and those flies were less fecund. In an experiment, where entire clutches were cross-fostered between nests, we found that the fecundity of the flies collected on nestlings was negatively correlated with the genetic mother's plumage spottiness. These results suggest that the ability to resist parasites covaries with the extent of female plumage spottiness. Among females collected dead along roads, those with a lot of black spots had a small bursa of Fabricius. Given that parasites bigger the development of this immune organ, this observation further suggests that more spotted females are usually less parasitized. The same analyses performed on male plumage spottiness all provided non-significant results. To our knowledge, this study is the first one showing that a heritable secondary sexual characteristics displayed by females reflects parasite resistance.

Filariopsis barretoi (travassos, 1921) (Nematoda: metastrongyloidea) lung parasite of primates from South America - taxonomy, synonyms and pathology

Nematodes and fragments of lungs from Cebus ssp., Callithrix jacchus (l.) and Saimiri sciureus (L.) were studied. The worms from Cebus and Callithrix must be called Filariopsis barretoi (Travassos, 1921). The names Filariopsis arator Chandler, 1931 and Filaroides cebi Gebauer, 1933 are synonymized to F. barretoi. The status of Filariopsis gordius (Travassos, 1921) remains uncertain. The pathology is described. The parasites are located in the pulmonary paranchyma, near the pleural surface, constituting nodules.

Dictyostelium discoideum as an expression host for the circumsporozoite protein of Plasmodium falciparum.

We have used the cellular slime mold, Dictyostelium discoideum (Dd), to express the Plasmodium falciparum circumsporozoite protein (CS), a potential component of a subunit vaccine against malaria. This was accomplished via an expression vector based on the discoidin I-encoding gene promoter, in which we linked a sequence coding for a Dd leader peptide to the almost complete CS coding region (pEDII-CS). CS production at both the mRNA and protein levels is induced by starving cells in a simple phosphate buffer. Variation in pH or cell density does not seem to influence CS synthesis. CS-producing cells can be grown either on their normal substrate, bacteria, or on a semi-synthetic media, without affecting CS accumulation level. The CS produced in Dd seems similar to the natural parasite protein as judged by its size and epitope recognition by a panel of monoclonal antibodies. We constructed a second expression vector in which the CS is under the control of a Dd ras promoter. CS accumulation can then be induced by external addition of cAMP. Such a tightly regulated promoter may allow expression of proteins potentially toxic to the cell. Thus, Dd could be a useful eukaryotic system to produce recombinant proteins, in particular from human or animal parasites like P. falciparum.

The genus lobatostoma (Trematoda: Aspidocotylea) in the pacific coast of South America, with description of Lobatostoma veranoi new species, parasite of Menticirrhus ophycephalus (Teleostei: Sciaenidae)

The presence of three aspidocotyleans trematodes in marine fishes from Perú and Chile is reported. One of them, Lobatostoma veranoi from the intestine of Menticirrhus ophicephalu (Sciaenidae) is considered a new species. Distinct characteristcs of the new species are:a cirrus sac smaller than the pharynx; tail overlapping posteriorly the ventral disk; testis in the last third of the body and the presence of 64-66 marginal alveoli. The two other species are Lobatostoma pacificum Manter, 1940 found in Trachinotus paitensis Cuvier, 1830 from Perú and Chile and Lobatostoma Anisotremum Oliva & Carvajal, 1984 from the intestine of Anisotremus scapularis (Tschudi, 1844) from Perú.