Higher Egg Output Research Articles

Epidemiological observations on helminth infections of calves in southern Ghana

This paper describes helminth infections in three groups of calves of different ages grazing naturally infested pastures from March 1987 to May 1988. Calves in which the faecal egg output was followed from birth showed Toxocara vitulorum eggs as early as two days after birth and maximum patency occurred after two months. The fall in Toxocara egg output coincided with a rise in that of the strongylates; Haemonchus spp., Trichostrongylus spp. and Oesophagostumum spp. The influence of rainfall in dictating strongylate nematode infection was clear with high egg output during high rainfall and low egg counts when the rainfall was lower. There was an indication that calves carry the infection from the end of the minor rainy season in November to the beginning of the next rains in March and then contribute to pasture contamination. However, calves born in December may remain uninfected until the onset of the rains.

Effects of an integrated control programme with ivermectin on growth, carcase composition and nematode infection of beef cattle in Argentina's western pampas

The effect of previous pasture management and ivermectin treatment on gastrointestinal parasitism, weight gain and carcase composition of steers was studied in the semiarid Pampeana region of Argentina from April 1986 to April 1987. Three groups, each of 15 weaned calves, were grazed on separate lucerne pastures. Group 1 control calves, which grazed paddocks previously grazed by nematode-infected weaners and yearlings with a high nematode egg output, were only medicated when heavy parasitism was recorded. Group 2 calves, which grazed paddocks previously infected by steers at least two and a half years old with low nematode egg output, were treated strategically with ivermectin. Group 3 calves, which grazed on ‘clean’ paddocks, were treated monthly with ivermectin. Group 1 calves showed heavy parasitism and parasitological parameters were higher than in groups 2 and 3. The liveweight gain responses of groups 2 and 3 were significantly greater than those of group 1 (P < 0 · 001) during autumn, winter and early spring. At the end of the study when cattle reached market condition, the liveweight gains of groups 2 and 3 were 74·1 and 81·9 kg, respectively, greater than group 1. Carcase analyses showed significantly greater weight and killing-out percentages in groups 2 and 3 than in group 1. Reduced total bone, muscle and fat weights were observed in group 1.

Echinostoma caproni in rats: worm population dynamics and host blood eosinophilia during primary infections with 6, 25 and 50 metacercariae and resistance to secondary and superimposed infections

Hooded-Lister rats were inoculated with 6, 25, 50 or 100 metacercariae of the intestinal trematode Echinostoma caproni. Worm establishment and the pattern of egg excretion were followed during the course of primary infections with 6, 25 and 50 metacercariae. Peripheral blood eosinophilia was followed at all infection levels. After 1 month, worm recovery and faecal egg output showed a gradual decline with increasing duration of infection. High worm burdens were expelled later than smaller worm burdens, and egg output persisted longer in animals exhibiting a high initial egg output. The level of blood eosinophilia increased with increasing degree of infection and with the level of egg output. A marked concomitant resistance to superimposed infection was observed on the challenge of rats harbouring 21- and 49-day-old infections with 50 metacercariae. In addition, rats were partially resistant to secondary infection at challenge day 14 following anthelmintic removal of primary 7-day-old infections with 50 metacercariae and were completely resistant at challenge day 7 following elimination of a primary 14-day-old primary infection.

The effect of repeated targeted mass treatment on the prevalence of schistosomiasis mansoni and the intensity of infection in Machakos, Kenya.

In a valley in Machakos District, Kenya, the entire population was surveyed in 1976 for the presence and number of eggs of Schistosoma mansoni in their faeces. All persons with 300 or more eggs g-1 faeces were then treated with a single dose of hycanthone, 1.5 mg kg-1 body-weight. A re-survey was carried out in 1977, followed by the treatment of all persons with 200 or more eggs g-1 faeces. After another re-survey in 1978, all persons with 100 or more eggs g-1 were treated. The final survey was carried out in 1981. It was found that the treatment of persons with a high egg output had a pronounced effect on the intensity of infection in the total population, but that, after a first considerable drop in the prevalence rate, further decreases were much smaller. Continuing moderate prevalence rates in very young children were an indication of continuing transmission.

Reproduction and fecundity of the musselmytilus edulis at helgoland (North sea)

The reproductive cycle of aMytilus edulis population in the lower tidal zone at the island of Helgoland from Spring 1980 to Summer 1981 is described. In both years the spawning period extended from the end of April until the end of June at water temperatures between 6° and 14°C. The gametes were built up again in autumn and most individuals were mature in February. Sex ratio did not differ significantly from 1:1. Fecundity, egg diameter and gamete weight of this and another population in the subtidal zone were assessed and size frequency distribution of shell lengths was established. Based on data of body weight prior to spawning, the following tendencies could be outlined: animals of the intertidal population had significantly smaller eggs than those from the subtidal area. Although the soft body biomass per unit area of the subtidal population was nearly double that of the tidal, their annual egg output was nearly the same (2.3 × 109 eggs m−2). This was achieved by a smaller size at the onset of sexual maturation (18 mm instead of 30 mm shell length) and a higher egg output at comparable shell lengths in the intertidal. In both populations, large animals contributed most to gamete production, although they did not necessarily dominate in biomass.

Worm burdens in cows: the effect of anthelmintic treatment on the parasite egg output

The effect on the nematode egg output of anthelmintic treatment with levamisole after parturition was studied in a group of 298 cows on four farms in the province of Groningen, and three farms in the province of Noord-Brabant (The Netherlands). Two faecal samples were taken, the first within 48 h post partum, and the second 14 days later. Half the number of cows were treated after the first sampling. Faecal examinations were made by culturing a fixed amount of faeces, counting the larvae, calculating an LPG (number of larvae per g of faeces) and making a larval differentiation. From the first sampling it became clear that with some exceptions egg output was generally low (mean LPG 7.9). Most of the cows (87.9%) were positive for Ostertagia spp. Of the other species, Trichostrongylus spp. were found in 47.7% of the samples and Cooperia puncatata in 30.5%. Less frequent were Bunostomun phlebotomum (13.1%), Oesophagostomum spp. (9.4%), Cooperia oncophora/surnabada (8.7%) and Haemonchus contortus (7.7%). The latter species was only found on farms in Noord-Brabant and was related to the grazing of sheep on the cattle pastures. In more than 60% of the cows in both provinces with an LPG-value above 20, C. oncophora/surnabada larvae were present, while H. contortus larvae were found in 50% of those cows in Noord-Brabant. Highest counts were generally observed in cows lactating for the first time, but sometimes individual cows of older age showed a high egg output. The highest LPG-value found in this study was 228, in a first-lactating cow. The second sample of treated animals, 14 days after the first, showed that the LPG was significantly reduced from 7.6-1.4 ( P < 0.001), while in the non-treated cows the reduction of the LPG was from 6.7-6.1, which proved to be not significant. However, all species seen prior to treatment were still present after treatment.

Morbidity from Schistosoma mansoni in a Puerto Rican community: a population-based study.

A population-based approach was used to investigate morbidity from Schistosoma mansoni in a rural community in eastern Puerto Rico that was representative of remaining endemic foci on the island. In 1974 the prevalence of infection 855 of 1,056 inhabitants was 32.7% and the geometric mean egg output was 17.6 eggs per gram. A standardized medical history was obtained, and physical and laboratory examinations were performed on 737 (70%) of the community residents. Quantitative S. mansoni egg counts were performed on 1 gram of feces with a modified Ritchie formol-ether concentration technique; other intestinal parasites were recorded on a semi-quantitative basis. Interviews and physical examinations were conducted "blind" to minimize observer bias, and statistical analysis was done on data from 149 infected subjects and 149 noninfected controls matched by age and sex. For subjects under 20 years of age the frequency of hookworm infection and trichuriasis and absolute eosinophilia was significantly higher in the infected group, but no difference was found in the frequency of signs and symptoms of schistosomiasis. For the subjects 20 years and over, the symptom "blood in the stool" was reported more frequently in the infected group, but hematocrit level did not differ between infected and noninfected controls. Although palpable livers were noted more frequently in infected (8) than in noninfected (1) subjects 20 years and over, further evaluation of these subjects cast doubt upon a causal role for S. mansoni. These data indicate that morbidity from S. mansoni infection in the community is low, a finding consistent with the apparent decline in S. mansoni morbidity in Puerto Rico during recent decades and the relatively low intensity of infection in this community. Nevertheless, because of the sporadic occurrence of S. mansoni-induced disease on the island, and because heavily infected subjects are clearly at greater risk of disease, we are recommending treatment for community residents with high egg output.

The epidemiology and consequences of Schistosoma mansoni infection in West Nile, Uganda : I. Field studies of a community at Panyagoro

A Jonam fishing community at Panyagoro, West Nile District, Uganda, was studied and the 235 people examined showed a very high infection rate with S. mansoni. The mean egg output of males over 5 years old was 1112 eggs/g. and of females was about half this level. High egg output levels were maintained into old age. Diarrhoea with blood and abdominal pain were extremely frequent. Hepatosplenomegaly, eosinophilia and anaemia were common and particularly occurred together in people who looked ill and had marked abdominal distension and ascites. Malaria was endemic but other possible causes of these findings were largely absent. Much disease is probably due to S. mansoni which is here causing disease of public health importance in sub-Saharan Africa.