Circadian Pattern of Cercarial Emergence inSchistosoma Mansoni(Platyhelminthes: Digenea) from IsolatedBiomphalaria Glabrata

Abstract

The present work aimed to compare the acrophases (peak hours) of emergence of Schistosoma mansoni cercariae among isolated individuals of the snail Biomphalaria glabrata. Laboratory stocks of melanic B. glabrata from the same biotope as the S. mansoni strain (Belo Horizonte, Minas Gerais) were used. Twenty-two snails individually exposed to five miracidia were tested. Chronobiological trials were performed outdoors after an acclimation period of at least a week. Three groups of snails were tested between November 1989 and April 1991. Cercarial emergence from individual isolated snails was quantified every 3 h for 3 consecutive days. In all trials, most cercariae were found to emerge during daytime (94.9%). Time series and chronograms showed recurrent peaks during the daytime. The periodogram suggested that 24 h was the period that best fitted cercarial emergence data in 90.9% of the snails. The single cosinor analysis confirmed 24-h rhythms in 95.5% of the snails. Acrophases of cercarial emergence among individual snails occurred between 14:15 and 17:02. They did not differ significantly. The population cosinor analysis indicated greater homogeneity in the 24-h rhythms of cercarial emergence than in the snail groups of each chronobiological trial. Acrophases of cercarial emergence occurred between 14:53 and 15:27 and did not differ significantly among all trials. Data from the three trials were pooled and analyzed using the population cosinor. This statistical method indicated a homogeneity in the 24-h rhythms of cercarial. emergence from all snails, with acrophase occurring around 15:00. Results showed that the acrophases of cercarial emergence of S. mansoni are similar among isolated B. glabrata specimens. Data support the hypothesis of a "gate" rhythm in the dynamics of cercarial production and emergence. It is suggested that the adaptive importance of the "gate" mechanism is associated with the concentration of cercariae in the water at times when the vertebrate is present, optimizing the contact between the parasite and the host. The emergence of some cercariae at night (5.1% of the total number of emerged cercariae) suggests a flexible "gate" that could be associated with a residual light effect or with experimental procedures in the laboratory.

Trichuris Burdens in Zoo-Housed Colobus guereza

“…Our data indicate that time of day and individual differences are associated with significant variations in epg of Trichuris spp. Previous researchers have noted periodicity in helminth transmission, e.g., with Schistosoma a circadian pattern occurs when cercariae are voided from their snail hosts and again when the matured eggs of Schistosoma are voided from their human hosts (Bogea et al 1996;Doehring et al 1983). For some helminths the periodicity enhances transmission under favorable conditions (Fingerut et al 2003).…”

Loa loa Microfilarial Periodicity in Ivermectin-Treated Patients: Comparison Between Those Developing and Those Free of Serious Adverse Events

“…The latter is similar to that of Aikat and Das, but it is simpler and can deal with non equidistant data (as it is the case in the present dataset). Cosinor analyses have been used in parasitology to characterize, for example, the pattern of cercarial emergence of Schistosoma mansoni from its intermediate host 40 and the periodicity of W. bancrofti mf. 41 Although rare, the possible occurrence of post-ivermectin Loa -related SAEs constitutes a major impediment in Figure 1.…”

Assessment of schistosomiasis, through school surveys, in the Forest Zone of Pernambuco, Brazil

“…The emphasis has been on the ecology and control of the mollusks that are the intermediate hosts (Barbosa 1992a,b, 1996, Barbosa & Barbosa 1994, 1996, Barbosa et al 1992, 1993, Bogéa et al 1996, Dannemann & Pieri 1989, 1991, 1993a, b, Favre et al 1995, 1997, Gazin et al 2000, Pieri 1995, Pieri & Dannemann 1996, Pieri & Thomas 1986, 1987, Randall et al 2001, Sarquis et al 1997, the ecological and epidemiological determinants of the disease (Barbosa 1992b, 1997, 1998a, b, Barbosa & Coimbra 2000, Barbosa & Gouveia 2000, Coutinho et al 1997, Gazin et al 2002, Gonçalves et al 1992, Simões-Barbosa et al 2001, and also the impact of chemotherapy treatment for infected individuals, in relation to the transmission dynamics of the disease , Favre et al 2002, Zani et al 2004). The knowledge resulting from these studies has made it possible to adapt the schistosomiasis evaluation and control strategies recommended by central health bodies -WHO at the worldwide level and the Health Surveillance Department of the Ministry of Health at the national level -to the regional characteristics and demands.…”