Seasonal Prevalence Patterns Research Articles

Seasonal Patterns in the Biology of Eubothrium salvelini Infecting Brook Trout in a Creek in Lower Michigan

A total of 392 brook trout, Salvelinus fontinalis, and 211 slimy sculpin, Cottus cognatus, was examined for Eubothrium salvelini (Cestoda) from May 1995 through September 1996 from Sweetwater Creek, Michigan. No seasonal pattern in prevalence, intensity, and abundance of parasites in trout and sculpin was determined. However a seasonal pattern in the length and percent gravid E. salvelini in brook trout suggests that recruitment of this parasite occurs during late summer and early fall. During this time the procercoid in the copepod intermediate host is expected to be available in the environment for fish to recruit, but a total of 6,399 copepods was not infected. Gravid worms were not found in slimy sculpin, suggesting it is a paratenic or dead-end host. Detailed studies on the biology of parasites may be more indicative of seasonal transmission patterns than studies that only measure prevalence, abundance, and intensity.

Seasonal variations in density of questing Ixodes ricinus (Acari: Ixodidae) nymphs and prevalence of infection with B. burgdorferi s.l. in south central Sweden.

Seasonal variations in the density of questing Ixodes ricinus (L.) nymphs and their prevalence of infection with Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner were studied during 1991-1993 at a locality in southcentral Sweden. The seasonal pattern of the density of questing I. ricinus nymphs was variable; there was a bimodal pattern with peaks of similar magnitude in 1991, a bimodal pattern with a small spring peak and a greater autumn peak in 1992, and a unimodal pattern with a spring peak and lower values during summer and autumn in 1993. The seasonal pattern of prevalence of Borrelia infection in questing nymphs was similar during all 3 yr, with a peak infection prevalence in late spring or early summer, followed by lower infection prevalences in late summer and autumn. There was a significant correlation between the monthly density of Borrelia-infected nymphs and the monthly density of nymphs. This suggests that, within a certain range of nymphal densities, it may be possible to assess the density of Borrelia-infected I. ricinus nymphs without examining nymphs for B. burgdorferi s.l.

Population biology of Proteocephalus macrocephalus (Creplin) in the European eel, Anguilla anguilla (Linnaeus), in two small rivers

Seasonal changes in populations of Proteocephalus macrocephalus (Creplin) were investigated for 17 months in the European eel, Anguilla anguilla (Linnaeus), in two rivers in Devon, SW England, but no clear seasonal patterns in prevalence and abundance were apparent. Population levels of the cestode are low in both localities, and it is suggested that natural population levels of P. macrocephalus may generally be low. However, growth and maturation of the cestode show marked seasonality with both occurring mainly in early summer.

The population biology of Camallanus lacustris (Zoega) in eels, Anguilla anguilla (Linnaeus), and their status as its host

The population biology of Camallanus lacustris (Zoega) and the status of the eel, Anguilla anguilla (Linnaeus), as its definitive host have been studied in a small Devon lake. No clear seasonal pattern in prevalence and abundance was observed, and recruitment of the new generation may occur in all seasons. However, reproduction exhibits some seasonality as adult nematodes were the commonest stage in the parasite population from early summer onwards and production of first‐stage larvae appeared to occur primarily during this period. These larvae were viable, and shown experimentally to be infective to copepods. The occurrence of the nematode and its development to full maturity in eels, the absence of its typical definitive host (Perca fluviatilis Linnaeus) from the lake and the absence of the nematode from other species of fish in the lake indicate that eels serve as the only, true definitive host of the nematode in this locality. It is suggested that account must be taken of this alternative host when the population of C. lacustris is investigated in the future.

Some comments on the aerobiology of fungus spores

Abstract While exposure/symptom relationships are relatively well-defined for pollen allergens, such relationships have not been clearly established for airborne fungus spores due to a lack of clearly defined seasonal patterns, prevalence of world-wide cosmopolitan fungi, and serious problems with sampling and identification. Ascospores and basidiospores have been least studied with respect to aerobiology, although both are clearly allergenic. Preliminary data on allergenicity and diurnal and seasonal prevalence patterns for selected ascospore and basidiospore types are presented.

Parasites of trout from the Au Sable River, Michigan, with emphasis on the population biology of Cystidicoloides tenuissima

Trout (212 brook trout, Salvelinus fontinalis, and 231 brown trout, Salmo trutta, Salmonidae) were collected from the Au Sable River, Michigan, and examined for parasites between April 1982 and July 1984. One hundred seventy-six brook trout and 153 brown trout were infected with at least one of the following parasites: Crepidostomum cooperi, Neascus sp., Eubothrium sp., Proteocephalus sp., Truttaedacnitis sp., Cystidicoloides tenuissima, Rhabdochona canadensis, Spinitectus gracilis, Epistylis sp., Trichodina sp., and Salmincola edwardsii. Cystidicoloides tenuissima, the most common and abundant species, did not exhibit a pronounced seasonal pattern in prevalence; mean intensity, however, was highest in July 1982, 1983, and 1984 in both trout species. The intensity of C. tenuissima increased as trout became older and then decreased in brook and brown trout 3 and 4 years of age, respectively. Data on the seasonality of S. gracilis and C. cooperi infecting trout are also presented. The muscles of trout were negative for parasites. Over 500 mayfly nymphs (Ephemeroptera) representing at least seven species were examined for parasites. Cystidicoloides tenuissima infected Ephemera simulans. Crepidostomum sp., Rhabdochona sp., and S. gracilis occurred in Hexagenia limbata.

Naididae (Oligochaeta) as hosts for mermithid nematodes (Enoplida: Mermithidae)

Naidid species Chaetogaster diaphanus, Chaetogaster diastrophus, Chaetogaster limnaei limnaei, Dero digitata, Dero nivea, Nais communis, Nais simplex, Nais variabilis, Pristina leidyi, Slavina appendiculata, and Stylaria lacustris were observed as paratenic and possibly intermediate hosts for larval mermithid nematodes from field collections. Mermithids were generally found in the anterior, dorsal region of the oligochaetes. Individual naidids were at most infected with two nematodes. No seasonal prevalence patterns could be firmly established owing to the sporadic occurrence of mermithid infections in the naidids.

Seasonal dynamics of Allopodocotyle boleosomi (Pearse, 1924) n. comb. (Digenea: Opecoelidae) in Wisconsin darters (Etheostomatinae)

Allopodocotyle boleosomi n. comb., created for Allocreadium boleosomi Pearse, 1924, is redescribed and its taxonomic history is reviewed. The purpose of our study was to determine seasonal population dynamics of A. boleosomi in O'Neil Creek darters. Etheostoma flabellare was most heavily infected with A. boleosomi. Etheostoma flabellare is one of the six species of darters occurring at a study site in O'Neil Creek, Chippewa County. Wisconsin. Seasonal changes in abundance and maturation of A. boleosomi in E. flabellare were studied for 14 consecutive months, and its occurrence in E. nigrum, E. caeruleum, E. zonale, Percina maculata, and P. caprodes was observed. Specimens of A. boleosomi were present in E. flabellare throughout the year, but displayed a distinct seasonal pattern of prevalence, relative density, and maturation. Most recruitment occurred in May and June and peak occurrence of gravid specimens was reached in July. Little growth or development of A. boleosomi took place during autumn, winter, or early spring. Each of the five other syntopic species of darters was less suitable as a host for A. boleosomi, some because of ecological differences and others perhaps because of physiological factors. Five additional species of helminths occurred in O'Neil Creek darters: Crepidostomum isostomum, Bothriocephalus formosus, Carnallanus oxycephalus, Pomphorhynchus bulbocolli, and Neoechinorhynchus sp.

Seasonal population dynamics of five species of intestinal helminths of the brook stickleback, Culaea inconstans

Seasonal changes in populations of five species of enteric helminths that parasitize the brook stickleback (Culaea inconstans) were studied during a 14-month period in Wisconsin. The trematodes Bunodera eucaliae, B. luciopercae, and immature Halipegus sp., the acanthocephalan Neoechinorhynchus pungitius, and the larval cestode Proteocephalus sp. each displayed pronounced seasonal patterns of prevalence in Sioux Creek sticklebacks. Bunodera eucaliae, the most abundant species, infected sticklebacks in early summer. By late summer, most B. eucaliae had completed egg production and were expelled from their hosts. Some B. eucaliae overwintered in sticklebacks and completed development in late spring. In contrast, B. luciopercae displayed low prevalence in sticklebacks and produced eggs at the coldest period of the year. The relative density of N. pungitius increased throughout fall and winter. These acanthocephalans were most numerous and attained maximum development in late spring. Unencysted metacercariae of Halipegus sp. parasitized sticklebacks in midsummer but thereafter declined in relative density. Sticklebacks possibly acted as paratenic hosts for H. eccentricus which occur commonly in Rana pipiens and R. clamitans in Sioux Creek. A few sticklebacks harbored Proteocephalus sp. plerocercoids in midsummer but this parasite was virtually absent throughout the remainder of the year.

Biting prevalence and malaria transmission patterns in the Anopheles punctulatus complex (Diptera: Culicidae) in Papua New Guinea.

Seasonal prevalence and malaria transmission patterns of Anopheles farauti, An. punctulatus and An. koliensis were studied in two coastal and two inland villages in the Madang district of northern Papua New Guinea. The monthly manbiting rates (average biting density of vector mosquitoes per man per night) were observed over a two-year period to establish typical seasonal prevalence patterns. Observations on the frequency of feeding and the human blood index were combined to derive the manbiting habit. A daily survival rate was determined from the dissection of mosquito ovaries by Polovodova's age-grading method. The extrinsic cycle in the mosquito was not observed, and the value for this parameter was extracted from the literature. All parameters were combined to estimate the monthly variations in vectorial capacity of each of the vector species, and the vectorial capacities of the individual species were added together to give a total monthly vectorial capacity of the punctulatus complex in each locality. The results showed that malaria transmission can be perennial, with a period of more intense transmission between August and January in the southern area, and between September and February in the northern. A period of very low transmission can be expected between February/March and July/August.

Seasonal Occurrence and Host-Parasite Relationships of Neoechinorhynchus saginatus Van Cleave and Bangham 1949 in the Fallfish, Semotilus corporalis (Mitchill)

The seasonal occurrence, population dynamics, intestinal distribution, and host specificity of Neoechinorhynchus saginatus infecting the fallfish, Semotilus corporalis, from the Oyster River, New Hampshire, were studied from June 1975 through July 1976 and March 1977 through December 1977. Neoechinorhynchus saginatus did not exhibit a clearly pronounced seasonal pattern in prevalence and mean intensity. Prevalence was 44% or higher in all months sampled. The number of parasites per examined fish differed significantly between June 1975 through July 1976 and March 1977 through December 1977. Gravid females and subadult N. saginatus were recovered throughout most of the sampling period. Neoechinorhynchus saginatus occurred throughout the intestine of fallfish, but the majority of acanthocephalans was recovered from the middle portion of the intestine. The intestinal distribution of females and males was similar. Gravid females were most common in the region of the first intestinal flexure below the fallfish's stomach. The sex ratio was found to be very close to 1 : 1. Both prevalence and mean intensity increased significantly with increasing size of fish. Although N. saginatus occurred in 4 other fish species, gravid worms were only recovered from fallfish.