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PubMed2001

Studies on the use of Yucca schidigera to control giardiosis.

The potential anti-giardial activity of a powdered preparation of Yucca schidigera (yucca powder) was investigated in vitro, in a modified adherence inhibition assay, and in vivo, by enumeration of trophozoites (intestinal) or cysts (fecal) in experimentally infected gerbils and lambs receiving oral doses of whole or butanol-extracted yucca powder. Yucca powder, butanol-, acetone- and chloroform-extracted powder, and the butanol-insoluble fraction of the powder were required in concentrations of 22, 15, 62, 135 and 250 microg/ml, respectively, to reduce in vitro trophozoite adherence by 50%. Ethyl ether extract exhibited no anti-giardial activity. Virtually no trophozoites were tolerant of butanol extract at >or=90 microg/ml. Butanol extract at 1500 microg/ml exerted effects on trophozoites similar to the nitroimidazole, metronidazole, at 40 microg/ml during a 27-h incubation. Reducing trophozoite adherence to 50% of the controls required 5-10h of exposure to butanol extract or metronidazole. Oral administration of butanol extract (6.1mg) or metronidazole (1mg) once daily for 3 days reduced the number of trophozoites in the small intestine of infected gerbils, significantly (P<0.05) in the jejunum and ileum, and numerically (P>0.05) in the duodenum (n=8). Oral dosing of 50mg of butanol extract in eight doses over 3 days reduced (P<0.05) trophozoites in the duodenum and jejunum, and eliminated them from the ileum. Including 4.5% (w/w) yucca powder in the diet did not alter Giardia trophozoite recovery from the duodenum or jejunum of infected gerbils, but trophozoite reduction (P=0.051) was observed in the ileum (n=9). Jejunum gut loop data were inconclusive, possibly due to insufficient duration of exposure of trophozoites to butanol extract. Compared to controls (0g yucca powder per day) lambs receiving 10g of yucca powder per day in their diet shed fewer (P<0.05) Giardia cysts in their feces after 5, 9, 12 and 19 days of treatment, but a corresponding decline in the prevalence of infection was not observed (n=10). After 26 days, Giardia infections persisted in 90% of the lambs in both treatment groups. At the dosing levels studied in vivo, yucca powder did not affect the extent of cyst shedding by experimentally infected lambs, but further purification and concentration of the saponin fraction from Y. schidigera may provide the anti-giardial effects observed in vitro and in dosing trials.

Administration, Oral↗
PubMed2003

The development of Trichostrongylus colubriformis larvae on a range of herbage species or on plots of differing topographical aspect.

Five "contaminations", where faeces containing Trichostrongylus colubriformis eggs were deposited on pasture and serially recovered, were used to compare the rate of decline of faecal mass and larval development. In the first three contaminations, faeces from a common source were deposited on swards of browntop (Agrostis capillaris cv Grasslands Muster), ryegrass (Lolium perenne cv Grassland Nui), white clover (Trifolium pratense cv Grassland Tahora), or onto bare ground in the late spring, summer or autumn. The last two contaminations were done on the north facing aspect or south facing aspect of hill country pastures in summer and autumn. Number of free-living nematodes (first- and second-stage larvae (L(1) and L(2)) and soil dwelling nematodes) and third stage larvae (L(3)) recovered from faeces were counted. In spring there was a significant (P<0.01) effect of sward type on the mass of faeces remaining, with greatest mass remaining on browntop and ryegrass 28 days later, and less on bare ground and white clover. In summer there were more (P<0.05) faeces remaining on browntop than on other herbages which had little faeces remaining and which did not differ one from another. In autumn there was a rapid decline in faecal mass. All faeces were gone from white clover and ryegrass swards by day 10 and from browntop and bare ground by day 14. The number of free-living nematodes did not differ markedly between seasons, ranging from 5 to 8.5% of eggs deposited. The number of L(3) recovered was low in spring ( approximately 0.4% of eggs deposited) and did not differ between swards. In summer, more (P<0.05) L(3) were recovered from faeces deposited on swards of ryegrass and white clover than from bare ground or browntop. Most L(3) were recovered from days 7 to 14 ( approximately 1.3% of eggs deposited). In the autumn, low numbers of L(3) were recovered from browntop on day 3 and ryegrass on day 7 (0.2% of eggs deposited) with virtually no L(3) recovered from faeces placed on white clover or bare ground. There were significant (P<0.001) effects of aspect on the amount of faecal mass remaining in both summer and autumn with less faeces remaining on the south facing aspect than on the north. This was particularly evident during the summer when virtually all of the faeces were intact on the north facing aspect but only 40% was remaining on the south on day 28. In the autumn, while faeces were completely gone from both aspects by day 28 but there were less (P<0.05) faeces remaining on the south facing aspect from days 3 to 18 than from the north. There was no aspect effect in either season on the number of free-living nematodes recovered which averaged 8-11% of eggs deposited. In both seasons a greater number of L(3) were recovered from faeces on the south facing aspect than on the north, particularly 3-10 days after faecal deposition. In summer the rise in L(3) recovered in faeces was more rapid on south facing aspect than on the north but both attained a maximum level of approximately 4% of eggs deposited. In autumn on day 3 there was a rapid rise on south facing aspect to approximately 21% of eggs deposited followed by a gradual decline on day 10 while on the north facing aspect numbers of L(3) recovered only attained 10% of eggs deposited.

Agrostis↗
PubMed1998

Serum immune response to Giardia duodenalis in experimentally infected lambs.

Twenty-three protozoan-free lambs were experimentally infected with Giardia duodenalis trophozoites at 6 weeks of age, while 24 controls lambs were not challenged. Weekly blood samples were taken and faecal cyst counts monitored for 11 weeks following infection. All experimentally infected lambs remained infected throughout the 11 week study period and control animals remained free of the parasite. Giardia-specific serum IgM, IgG and IgA antibody titers were determined weekly in 10 infected and 10 control lambs by enzyme-linked-immunosorbent assay (ELISA). Western blot analysis of serum immunoglobulins to proteins derived from four different Giardia isolates (S2, WB, D3 and NF) was performed. Weekly mean control IgM, IgG and IgA titers did not change throughout the study. Infected lambs showed no difference in IgM titers between weeks 0 and 11, but IgG and IgA titers of infected lambs differed from the preimmune (week 0) serum titer at weeks 5, 7, 9, 11 and weeks 5, 9 and 11 respectively. SDS polyacrylamide gel electrophoresis analysis showed homogeneity in the proteins of the four Giardia isolates. Antigenic proteins were also similar for all four isolates; however, the proteins recognized by IgM, IgG and IgA antibodies differed. The weak immune response of lambs to Giardia may account for the chronic nature of this disease in sheep.

Animals↗
PubMed1999

Integrated and biological control of parasites in organic and conventional production systems.

Organic and other non-intensive animal production systems are of growing importance in several countries worldwide. In contrast to conventional farms, parasite control on organic farms is affected by several of the prescribed changes in management e.g. access to the outdoors in the summer and in most countries, a ban on preventive medication, including use of anti-parasiticides. Organic animal production relies heavily on grazing, and pasture or soil related parasites are thus of major importance. Several studies in northern temperate climate have indicated that outdoor production of pigs, primarily sows, and laying hens results in heavier and more prevalent helminth infections compared to conventional intensive production under indoor conditions. In organic dairy cattle, parasitic gastroenteritis in heifers may be more prevalent. In a short to medium term perspective, integrated control may combine grazing management with biological control using nematophagous micro-fungi, selected crops like tanniferous plants and on conventional farms, limited use of anti-parasiticides. At present, the non-chemotherapeutic control of pasture related infections is based mainly on grazing management strategies. Preventive strategies, where young, previously unexposed stock, are turned out on parasite-free pastures, can be used for grazing first season dairy heifers and in all-in-all-out poultry production. Evasive strategies aim at avoiding disease producing infections of a contaminated area by moving to a clean area and may be relevant for ruminants and pigs. In cattle, effective control of nematodes can be achieved by repeated moves of the herd or alternate grazing with other species. High stocking rates seem to be an important risk factor. In pig production, the effect of paddock rotation on parasite infections is largely unknown and studies are warranted. Control of nematodes by larvae-trapping fungi, or perhaps in the future by egg-destroying fungi, looks promising for ruminants and certain monogastric animals but delivery systems and practical dosing regimes integrated with grazing management have to be developed. In conclusion, good prospects are expected for acceptable parasite control without a heavy reliance on anti-parasiticides through integration of the above mentioned procedures but future studies are needed to confirm their efficacy under practical farming conditions.

Animal Husbandry↗