The transstadial transmission of Babesia caballi by Rhipicephalus evertsi evertsi

Rhipicephalus evertsi evertsi larvae were fed on the ears of rabbits. Seven days after larval infestation, unfed, newly moulted nymphae were manually removed to infest a splenectomized donkey showing a patent Babesia caballi infection. Engorged nymphae were collected from the donkey and the ensuing adult ticks were placed on a susceptible horse. The horse contracted a B. caballi infection showing a prepatent period of 19 days after tick infestation. A very low parasitaemia, (highest score 2), which was patent for only 10 days, was recorded. The lowest packed cell volume recorded was 16%.     

The interaction between the immune response of rabbits to heterologous antigens and a primary infestation with Rhipicephalus evertsi evertsi

Rhipicephalus evertsi evertsi feeding on hosts inoculated with sheep red blood cells (SRBC) and bovine serum albumin (BSA) suppressed the primary antibody response to the two antigens. In addition, while the ticks paralysed most hosts in the studies, fatality associated with this toxicosis occurred only in rabbits which had received SRBC, either alone or with BSA. Only those hosts inoculated with BSA developed any resistance against the ticks, manifested by a slight reduction of engorged weights and development of anti-tick antibodies. These results suggest that R. e. evertsi infestation induces a degree of reduced host immune responsiveness to heterologous antigens.     

Resistance to Rhipicephalus evertsi evertsi in immunosuppressed rabbits

Rabbits treated with goat anti-rabbit thymocyte serum acquired less resistance to Rhipicephalus evertsi evertsi infestation than untreated controls. This inferior resistance was manifested as higher engorged weights of ticks and higher biotic potential, undue persistence of the ticks on the hosts and poor anti-tick antibody and delayed-type hypersensitivity responses. These observations highlight the significance of host T-cells in mediating resistance of ticks.     

The effects of non-specifically activated immunity in rabbits on primary infestation with Rhipicephalus evertsi evertsi

The secondary antibody response to sheep red blood cells and bovine serum albumin (BSA) was measured in rabbits infested with adult Rhipicephalus evertsi evertsi. The response was reduced (particularly for BSA) but still displayed anamnestic characteristics. Resistance against ixodid ticks associated with antibodies detected by gel diffusion and enzyme linked immunosorbent assay techniques early in the primary challenge was acquired by the immunized hosts only. This suggests that a non-specifically activated immune system enables hosts to develop rapid resistance against tick parasitism.     

Serum antibody to Sarcoptes scabiei and house dust mite prior to and during infestation with S. scabiei

In this study, serum antibodies to Sarcoptes scabiei var. canis (SS), Dermatophagoides farinae (DF), and D. pteronyssinus (DP) were determined in 19 healthy, random-source dogs prior to infestation with scabies then again during a primary infestation, cure and challenge infestation with scabies. Prior to scabies infestation, serum of 11 dogs contained faintly detectable amounts of IgE and/or IgG to proteins in SS extract, probably resulting from sensitization to dust mites that share cross-reactive antigenic epitopes with SS. After becoming infested with scabies, the response to SS antigens became stronger with antibodies appearing to more antigens as the scabies infestation progressed. Three of the newly recognized proteins were 170, 155 and 142/133 kD and could be used in a diagnostic test since antibodies to them appeared during the primary infestation.In addition, during the primary infestation, 14 of 15 dogs developed IgE to 1–11 new SS proteins in addition to an increase in IgE binding to those proteins recognized prior to infestation. Overall, the strongest antibody responses (IgE and IgG) were exhibited during cure of the first infestation, when dead mites were still present in the stratum corneum. As expected, the antibody response was strong and rapid during challenge when the infestation self-cured. The immunogenic SS proteins identified by serum antibody binding during challenge, when the hosts self-cured, are candidates for inclusion in a vaccine. These candidate proteins are 200, 185, 170, 155, 142/133, 112, 97, 74, 57, 45/42, 32 and 22 kD.Some of the proteins in SS that exhibited new or increased antibody binding during the experiment also had IgE and IgG binding to proteins with similar molecular weights in DF and DP extracts. These results illustrate the difficulties involved in understanding and interpreting serum antibody for developing a serological test for the diagnosis of scabies, isolating relevant SS antigens that could be included in a vaccine for prevention of scabies, and for understanding the immune response mechanism to scabies.     

Detection of immune response in rabbits infested with Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi

Two groups of rabbits infested repeatedly with Rhipicephalus evertsi evertsi and R appendiculatus acquired resistance as evidenced by reduced ectoparasite engorged weights and development of anti-tick antibodies in the hosts. The enzyme-linked immunosorbent assay (ELISA) using salivary gland antigens of R appendiculatus was able to detect antibody responses to both the homologous and heterologous tick challenges. It was concluded that the immune response in hosts infested by these two tick species stimulates the production of antibodies which show cross reactions.     

Difficulties to control natural infestation with Otobius megnini (Acari: Argasidae) nymphs in cattle with systemic biocides

A study was carried out to determine the efficacy of topical eprinomectin against nymphal infestation of Otobius megnini in cattle, where a group of 14 individuals were treated with a dose of 0.5 mg/per kg of body weight applied on the dorsal midline, and a group of 14 individuals remained as control. Tick burdens between treated and control groups showed no statistically significant differences (P > 0.05), and the mortality of the nymphs was similar in both groups (P: 0.828). All females obtained from nymphs of both groups were able to copulate with males from the corresponding group and laid eggs that produced visually normal larvae. The failure of eprinomectin and other biocides applied per os or by injection to control nymphs of O. megnini in cattle indicate that sanitary measures and applications of biocides into the ears would represent the most reasonable approach to control of this tick on cattle.     

Prevalence of Bovine Dermatophilosis in a Tropical Highland Region of Ethiopia

A study was made of bovine dermatophilosis on 540 animals at a high altitude (2400–2500 m above sea level) in Ethiopia. Eighty-two (15.4%) of the animals were affected by the disease which was more prevalent in local animals than was previously assumed. There was a significant (p<0.05) difference in the prevalence among different age groups. However, the difference in the prevalence of the disease between males and females was not significant (p>0.05). Associated risk factors included the relatively high average annual rainfall and humidity, tick infestation (76%) and management, related to the mixed crop-livestock production system. The possible impact of the disease on Ethiopian agriculture is indicated.     

Studies on Cephalopina titillator,the Cause of 'Sengale' in Camels (Camelus dromedarius) in Semi-arid Areas of Somali State,Ethiopia

The overall prevalence rate of Cephalopina titillator in 778 slaughtered camels was 71.7%, 55% in males and 85% in females. The mean larval counts in infested camels were 26.7±25.9 and 34.6±30.8, for males and females, respectively. There were highly significant differences (p<0.001) in the number of larvae in camels of different ages and sexes and also between the wet and dry seasons. The average time to pupate was 4.9±4.6 minutes, and the pupation period was 21±2.4 days. The major gross lesions observed were congestion of the pharyngeal mucosa with profuse secretions, and haemorrhage in early cases. In some cases, there were ulcer-like lesions and nodules, which contained pus. The dominant microscopic lesions were infiltration of the lamina propria by eosinophils, lymphocytes and macrophages, hyperplasia of the stratified squamous epithelium, necrotic changes in the mixed glands and desquamation of epithelial cells. A survey using questionnaires revealed that all the camel owners called the disease caused by infestation with C. titillator `Sengale' and that 87% of them considered that infestation with these larvae results in reduced milk production and body weight. The major clinical signs of the disease were sneezing and expulsion of larvae (68%), abnormal movement of the head (45%), grooming (44%), nasal discharge (40%), poor appetite (26.7%), difficulty in breathing (18%), and sometimes bleeding from the nostrils (18%) and coughing (27%).     

Stage specific mortality and humoral immune responses during pulse and trickle infestations of the common cattle grub, Hypoderma lineatum (Diptera: Oestridae)

Stage specific survival of larvae and pupae of the common cattle grub, Hypoderma lineatum de Villers, was compared in cattle artificially infested with larvae delivered by subcutaneous injection as a single infestation of 100 larvae, in trickle infestations of either two doses of 50 larvae, separated by 15 days, or in four doses of 25 larvae, separated by 9, 6, and 6 days, respectively. The duration of the migratory and 'warble' phases were also compared between treatments. The kinetics of the antibody response was monitored throughout the larval development by ELISA. No difference was noted in the level of antibodies among the three treatments. Mortality of first-instars differed among the infestation groups with mortality in the single pulse infestation group相似文献   

Humoral antibody response of rabbits to Rhipicephalus appendiculatus infestation

Rabbits infested four times in succession with adult Rhipicephalus appendiculatus developed anti-tick antibodies, demonstrated by the enzyme-linked immunosorbent assay, following primary infestation and increased by subsequent infestations. Maximum antibody activity was detected after the third infestation while lower ixodid engorged weights occurred from the second infestation onwards. The antibody activity stimulated by the fourth application of ticks was slightly less than that of the third infestation. A slight reduction in antibody activity occurred in the hosts during a tick-free period of 24 days after the third challenge.     

Impact of previous infestation on dynamics of circulating hypodermin C in cattle artificially infested with Hypoderma lineatum (Diptera: Oestridae)

Four groups of cattle were artificially infested with 50 first instar Hypoderma lineatum after either a primary natural infestation or in the absence of a primary infestation. In two groups the primary infestation had been terminated by the application of either an organophosphate insecticide or a macrocyclic lactone parasiticide. Circulating hypodermin C and specific antibodies were measured for 40 weeks after the artificial infestation. Stage specific mortality of the larvae was also monitored. Previously uninfested cattle exhibited typical antibody and antigen profiles during the infestations. Antibodies were first detected on Week 7 p.i., they rose to maximum values between Weeks 24 and 25, then declined as larvae reached the back. A second peak occurred at Week 32 and antibody remained more less constant thereafter. Previously infested groups exhibited a dramatic anamnestic response by Week 3 p.i. with antibody levels peaking at Week 8. A second peak was noted between Weeks 24 and 26 p.i. after which antibody levels declined and then remained relatively stable. The dynamics of circulating hypodermin C in the previously infested cattle resembled those in the previously uninfested cattle. Mortality of first instars did not differ among the four groups. Similarly mortality of second and third instars, in the warble, did not differ although there was a tendency for higher mortality in the previously infested, untreated group. These results reinforce previous work demonstrating the development of a significant immune response during the primary infestation that is reflected in the rapid and substantial production of antibodies upon re-infestation. It is significant that a challenge model using subcutaneous injection of newly hatched first instars avoids host immune responses in the skin that result in substantial larval mortality. The current data also support the concept that migrating first instars induce significant reduction in host immune response. There is a peak of antibody production as antigen levels peak during first instar migration to the back. As larvae molt to the second instar and antigen production ceases there is a persistence of antibody which suggests release of the immune response from the suppression induced by the first instar secretory antigens.     

Studies on the ability of different strains or populations of female Rhipicephalus evertsi evertsi (Acarina:Ixodidae) to produce paralysis in sheep

Simultaneous infestation of 3-6 month-old Black-head sheep with 15 South African wild strains of Rhipicephalus evertsi evertsi males and females as well as a strain from Rwanda clearly showed that all strains are capable of inducing paralysis. Assessment of the infestation-rate of engorging female ticks during the period that their mass ranged between 15 and 21 mg/kg sheep body mass indicated that toxicity is quantitatively identical and exhibits no intraspecific gradations. The period between the beginning of infestation to the manifestation of the first clinical symptoms is, however, strain dependent: 4 days for ticks from Warmbaths, and at least 5 days for all other strains.     

Effect of a single dry season anthelmintic treatment of N'Dama cattle on communal pastures in The Gambia

The effect of a single anthelmintic treatment of cattle during the early dry season was studied. One hundred and sixty-six N'Dama cattle, 1–3 years old, were selected from five herds. There were 65 males and 101 females divided into two groups of 83 animals each. One group was treated with fenbendazole at 7.5 mg/kg body weight by mouth in November 1992; the other group remained as the untreated control. At monthly intervals from November 1992 to April 1993, each animal was weighed and the number of eggs/g of faeces (epg) was determined. The infective larvae (L3) were examined following culture of pooled samples from each group of animals. In April 1993, 6 animals (3 treated and 3 controls) from the herds under study were necropsied. The difference in the weight gains (4.6 kg) of the two groups was highly significant (p<0.0001). The difference in the weight gains and the epg between the treated and control groups was influenced by the age of the animals. Of the treated animals, one contained no nematodes, one contained only 25Oesophagostomum radiatum, and the third contained 25Cooperia L4. The three untreated animals were all infected. It was concluded that the treatment in early dry season, with an anthelmintic effective against both adults and larvae, led to a significant reduction in egg counts, to elimination of adults and hypobiotic larvae and, consequently, to an increase in the body weight gain by the treated animals.     

Effect of dietary protein on the regulation of populations of Nematodirus battus by lambs

Two groups of seven and two groups of six lambs were offered either a complete basal ruminant diet (13·2 per cent crude protein [ ]) (groups 2 and 4) or the same diet supplemented with fish meal (18·3 per cent ) (groups 1 and 3). Groups 1 and 2 were infected daily for seven weeks with Nematodirus battus larvae (L₃) and groups 3 and 4 served as uninfected challenge controls. All the groups were treated with anthelmintic in the eighth week, challenged with a single dose of 30,000 N battus L₃ one week later and killed nine days after the challenge. Although protein supplementation tended to enhance the regulation of the population of N battus in the lambs which had been infected continuously, the effect was not statistically significant. The worm burdens in both the groups of previously infected lambs were significantly reduced both in number and size (P<0·001) and they had a lower proportion of male worms than the uninfected challenge controls. The lambs could be segregated into high or low responders on the basis of their worm burdens, and there was a significant reduction in worm burdens (P<0·001) and size (P<0·01) in parallel with the lambs' responsiveness. The identification of high and low responders shows that when the dietary protein supply is adequate the predominant effect of the host on the pathogenicity of its parasites is the host's genetically-determined susceptibility.     

A model to simulate the effect of vaccination against Boophilus ticks on cattle

In this study, serum antibodies to Sarcoptes scabiei var. canis (SS), Dermatophagoides farinae (DF), and D. pteronyssinus (DP) were determined in 19 healthy, random-source dogs prior to infestation with scabies then again during a primary infestation, cure and challenge infestation with scabies. Prior to scabies infestation, serum of 11 dogs contained faintly detectable amounts of IgE and/or IgG to proteins in SS extract, probably resulting from sensitization to dust mites that share cross-reactive antigenic epitopes with SS. After becoming infested with scabies, the response to SS antigens became stronger with antibodies appearing to more antigens as the scabies infestation progressed. Three of the newly recognized proteins were 170, 155 and 142/133 kD and could be used in a diagnostic test since antibodies to them appeared during the primary infestation.

In addition, during the primary infestation, 14 of 15 dogs developed IgE to 1–11 new SS proteins in addition to an increase in IgE binding to those proteins recognized prior to infestation. Overall, the strongest antibody responses (IgE and IgG) were exhibited during cure of the first infestation, when dead mites were still present in the stratum corneum. As expected, the antibody response was strong and rapid during challenge when the infestation self-cured. The immunogenic SS proteins identified by serum antibody binding during challenge, when the hosts self-cured, are candidates for inclusion in a vaccine. These candidate proteins are 200, 185, 170, 155, 142/133, 112, 97, 74, 57, 45/42, 32 and 22 kD.

Some of the proteins in SS that exhibited new or increased antibody binding during the experiment also had IgE and IgG binding to proteins with similar molecular weights in DF and DP extracts. These results illustrate the difficulties involved in understanding and interpreting serum antibody for developing a serological test for the diagnosis of scabies, isolating relevant SS antigens that could be included in a vaccine for prevention of scabies, and for understanding the immune response mechanism to scabies.     

Number of services and the reservice intervals in relation to suboptimal reproductive performance in female pigs on commercial farms

This study investigated the associations of the number of services, reservice intervals (RI), parity, and weaning-to-first-mating intervals (WMI) with farrowing rate and pigs born alive (PBA) on commercial farms. The selected 117 farms included 115,442 service records and 93,867 farrowing records in 54,502 female pigs (females). A service was defined as one or more mating events within a 10-day time period of estrus. The number of services was categorized into three groups: non-return to service, first reservice, and second or later reservice. The RI was divided into 8 seven-day interval groups from 11 to 66 days and a group of 67–150 days. The effects of the number of services, RI, WMI, and parity on farrowing rate and PBA were analyzed by using the mixed-effects models. The frequency distributions of non-return to service, first reservice, and second or later reservice groups were 88.6, 9.7, and 1.7%, respectively. Farrowing rate decreased by approximately 18% with each service (P < 0.05). Reserviced females exhibited a different reproductive performance as compared to non-return to service females depending on parity and WMI. In the non-return to service group, sows with WMI 7–12 days had the lowest farrowing rate (P < 0.05). Meanwhile, in the first and second or later reservice groups, no differences between the WMI groups were found in farrowing rate. At parity 1 and 2, the first reservice group had the most PBA (P < 0.05). However, at parity 0, 3–5, and ≥ 6, no differences between the number of service groups were found in PBA. In the WMI 0–6 and 7–12 day groups, the first reservice group had the most PBA (P < 0.05). The mean of RI was 44.5 ± 0.28 days in 13,183 reservice records. RI decreased from 47.4 to 39.2 days as parity increased from 0 to ≥ 6 (P < 0.05). The frequency distributions of the RI 18–24, 39–45, and 67–150 days were 39.3, 12.4, and 18.8%, respectively. Gilts had lower proportions of the RI 18–24 days and higher proportions of RI 67–150 days than sows at parity 3–5 (P < 0.05). No differences between RI groups were found in farrowing rate and PBA. Increasing farrowing rate in non-return to service females and minimizing RI in females at low parity improved herd productivity.     

Susceptibility to Tropical Theileriosis of Calves Born to Dams Immunized with Theileria annulata (Hisar) Cell Culture Vaccine

The susceptibility/immune status to tropical theileriosis of calves born of immunized dams was evaluated. Six cows were vaccinated with the Theileria annulata cell culture vaccine in the eighth month of pregnancy. Sera from the immunized dams exhibited very high post-vaccination antibody titres as determined by the indirect fluorescent antibody (IFA) test. The calves born to these dams did not show antibodies against T. annulata at the time of birth (IFA titres of <1:20). The new-born calves were fed colostrum from their mothers and were challenged with T. annulata-infected ground tick supernate at 5–7 days of age. All the calves developed fever (from day 5–6 onwards) and parasitological reactions (from day 8–9 onwards) after challenge. There was a significant decrease in the haemoglobin and packed cell volume of the calves after challenge. All the calves showed signs of acute theileriosis by day 9–10 after challenge and had to be treated with buparvaquone in order to save their lives. The study indicated that detectable levels of anti-theilerial antibodies were not transferred from immune dams to their offspring. All the calves born to immunized dams were fully susceptible to theileriosis and thus themselves needed vaccination.     

The distribution ofParascaris equorum eggs in the soil profile of bare paddocks in some Norwegian studs

Fifteen bare paddocks, which consisted of soil only and were located on 12 different studs, were examined for their content ofParascaris equorum eggs in the upper 15 cm of the soil profile. The paddocks were classified into three different groups according to the type of soil: clayey soil (A), morainic soil (B) and gravel or gravel-like sand (C). Soil profiles were collected down to a depth of 15 cm and were divided into three layers: 0–5 cm (D1), 5–10 cm (D2) and 10–15 cm (D3). The eggs in each layer were counted and identified as infective or noninfective eggs. The paddocks in group C, which had good drainage conditions, had significantly lower numbers of eggs in the whole profile and in D1 and D2 than the paddocks in groups A or B. Furthermore, there was a significantly higher proportion of the total egg count present in D3 in the group C paddocks. This may have been due to a higher degree of passive transportation of eggs down the profile in the gravel or gravel-like sand. Even though there was a significantly higher proportion of infective eggs in the soil from the group C paddocks, the lower total numbers of eggs resulted in a lower total number of infective eggs in those paddocks. The study showed that the soil type was an important factor in determining the content ofP. equorum eggs in the upper layer of the soil profile in bare paddocks and consequently for the potential infestation of horses withP. equorum.     

First reported case of Hypoderma diana Brauer, 1985 (Diptera: Oestridae)-associated myiasis in a horse in Germany

A massive infestation with warble fly larvae was observed in a mare in Lower Saxony, Germany. From a herd of 20 horses, only a single mare accidently escaped the routine treatment with macrocyclic lactone in autumn and showed the myiasis infestation next year in January. Eighteen subcutaneous nodules were found on the back (n = 2), ribs (n = 3), flank (n = 5) and croup (n = 8). Deer, the specific hosts of the warble fly Hypoderma diana, was abundant on this farm and some other risk factors for the hypodermiosis are discussed herein. This is the first report of myiasis caused by H. diana in horses in Germany. This massive warble fly infestation in a horse in Germany reported here is important to alert equine health professionals concerning the prevention of this disease in the routine parasite control programme.