Prophylactic and persistent efficacy of doramectin against Cochliomyia hominivorax in cattle

Homeopathic Sulphur Ointment as Adjuvant in the Treatment of Sheep with Myiasis by Cochliomyia hominivorax (Diptera: Calliphoridae): A Case Series

BACKGROUND

 Myiasis by Cochliomyia hominivorax (Diptera: Calliphoridae) is a serious problem in animal health. Homeopathic Sulphur presents similarity with the clinical presentation verified in these cases and has already shown in vitro efficacy on the blowfly that causes this pathology. This article presents the report of a series of clinical cases of myiasis by C. hominivorax in sheep that underwent adjuvant treatment with homeopathic Sulphur and presents a theoretical-scientific discussion of biological events related to the clinical treatment of the condition.

PATIENTS

 Seven naturally occurring myiases affecting sheep from an experimental farm were treated by an ointment impregnated with the homeopathic medicine Sulph 12cH, used as adjuvant after the manual removal of accessible larvae from the wound during wound cleaning. The animals were treated daily and evaluated clinically until complete healing of the lesions. Clinical information on the evolution of the inflammatory and scarring process was collected. Blood counts and bacteriological examinations were performed before and after topical homeopathic treatment.

RESULTS

 The homeopathic ointment Sulph 12cH was able to inhibit the development of parasitic C. hominivorax larvae and promote tissue repair and healing in naturally occurring myiasis in the sheep of this study.

CONCLUSION

 The homeopathic medicine Sulphur, formulated as an ointment, may be a useful new and adjuvant therapeutic option for treating myiasis in animals.

Dacryoadenitis caused by Cochliomyia macellaria (Diptera: Calliphoridae) in a sambar deer (Rusa unicolor) in Rio de Janeiro, Brazil

Flies of the genus Cochliomyia frequently cause myiasis in the Americas during the hot and humid climate, which favors the development of the parasite's life cycle. A three-year-old female sambar deer (Rusa unicolor), originated from a conservation farm in the municipality of Casimiro de Abreu, Rio de Janeiro state, Brazil, was presented for a necropsy. Grossly, a nodular wound in the right lacrimal gland was observed, with many intralesional larvae. The histopathological evaluation of the injured lacrimal gland revealed maggots surrounded by areas of necrosis and inflammation. Specimens were collected for parasitological examination. Morphologically, larvae were identified as Cochliomyia macellaria (Diptera: Calliphoridae). It is suggested that adult C. macellaria was attracted to the site of infestation by glandular secretion. The present study shows the first report of secondary myiasis by Cochliomyia macellaria in deer.

In vitro control of the camel nasal botfly, Cephalopina titillator, with doramectin, lavender, camphor, and onion oils

Camels are very important livestock particularly in arid and semiarid lands. The oestrid fly, Cephalopina titillator (Clark), causes nasopharyngeal myiasis in camels, and it is widely distributed in many camel breeding areas triggering health hazards and severe economic losses in camels. The prevalence of infestation of camels (slaughtered at Tokh's slaughterhouse, Qalyubia Governorate, Egypt, during the period from September 2011 to March 2012) was 41.67 % (100 out of 240). Most infested camels developed clinical signs of nasal discharge, restlessness, loss of appetite, difficulty in breathing, frequent sneezing, and snoring. Postmortem examination of infested camels explained that breathing of the animal is greatly impaired because of blockage of the nasopharynx by larvae and/or mucofibrinous secretions. The larval count per camel ranged from 1 to 250 (mean 28.45 ± 6.48). In vitro larval immersion tests were carried out to determine the efficacy of doramectin (0.003 %) as well as some essential oils (50 % each) such as lavender, camphor, and onion oils against the second and third larval stages (L2 and L3) of C. titillator. Another trial had been done for imitating what could happen if the area around camels were treated with an insecticide or an insect repellent. All treated L2 died 18 h posttreatment (PT) with both doramectin and lavender, and 100 % mortality was reached for L3 after 24 and 30 h PT with lavender and doramectin, respectively. Doramectin and lavender induced the highest response against C. titillator as their lethal time (LT50) values after treatment of L2 were 3.40 and 3.60 h, respectively, and those of L3 were 4.99 and 5.53 h, respectively. Against both L2 and L3 of C. titillator and based on LT50 values of onion oil and those of other applied materials, doramectin and lavender oil were four times more effective than onion oil, and camphor oil was two times more effective than onion oil. Based on LT50 values of essential oils and those of doramectin, as a reference substance, the relative speed of efficacy indicated that camphor and onion oils were, respectively, two and four times less effective than doramectin and lavender. With regard to fumigant technique, neither the insecticide, New Pyrosol, nor the insect repellent, Keto, was effective in controlling C. titillator larvae. Our results indicated that doramectin and lavender could be selected as drugs of choice for controlling C. titillator, but it is not permitted to use doramectin on dairy animals during lactation. Lavender (50 %) has a great potential to be developed as a novel larvicide and could be used as nasal drench against nasal botfly which will reflect on camel production and the national economy.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against myiasis causing parasites on ruminants

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of efficacy of ectoparasiticides against the myiasis causing parasites of ruminants. These guidelines specifically focus on larvicidal efficacy against myiasis causing flies. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies for defining therapeutic and persistent efficacy. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the world-wide adoption of standard procedures.

Screwworms

New World and Old World screwworms pose threats to the livestock industry in the United States and other countries. Diligence on the part of veterinarians, physicians, and their respective staffs is essential to protect the livestock industry.

Assessment of cypermethrin and doramectin for controlling wohlfahrtiosis in Crete

The fleshfly, Wohlfahrtia magnifica, became an animal health problem in Crete, Greece, during 1999, causing outbreaks of wohlfahrtiosis throughout the main livestock producing regions of the island. The aim of this study was to determine the efficacy of commercially available drugs in order to design control strategies against wohlfahrtiosis. The test substances were cypermethrin and doramectin sc. The test animals were randomly divided between three groups (30 in each): one treated with cypermethrin pour-on, one treated with doramectin and one untreated controls. The trial lasted 45 days and the animals were inspected daily for natural infestations by W. magnifica. The first infestations were recorded on the 5th, 13th and the 23rd day in the control, cypermethrin and doramectin groups, respectively. There was a statistically significant difference between the survival curves for doramectin and the control group up to day 40, but not at the end of the study.

Erradicação ou manejo integrado das miíases neotropicais das Américas?

A erradicação da bicheira, Cochliomyia hominivorax dos EUA, da América Central e do Norte da África tornou-se uma realidade criando e liberando machos estéreis. Por que nos não decidimos também erradicar este inseto da América do Sul? Antes de tomar uma atitude corajosa, nós discutiremos neste trabalho as razões científicas, ecológicas e econômicas. O berne, Dermatobia hominis não tem sido erradicado de nenhum pais, devido a que não dispomos de técnicas para sua criação massal em dietas artificiais. Estão faltando também estudos sobre a dispersão, comportamento sexual e sítios de agregação dos adultos no campo. Devido a que as miíases continuarão sendo controladas basicamente com inseticidas, recomendações para manejar a resistência aos inseticidas e estudos sobre métodos alternativos são discutidos visando um Manejo Integrado do berne e da bicheira com fundamentos ecológicos.

Efficacy of macrocyclic lactones for the control of larvae of the Old World screw-worm fly (Chrysomya bezziana)

OBJECTIVE

To assess the efficacy of four macrocyclic lactones for the control of larvae of the Old World Screw-worm Fly (OWS), Chrysomya bezziana, and to examine the effects of excreted residues on the dung fauna.

ANIMALS

100 heifers were divided into five groups of 20 animals. One group remained untreated, whereas the other groups were treated respectively with pour-on formulations of moxidectin, eprinomectin or doramectin, or a sustained-release bolus of ivermectin.

PROCEDURES

At intervals of 1 to 15 weeks after treatment, five cattle from each group were challenged with newly-laid eggs of OWS. The efficacy of each treatment was determined 48 h later by comparing the number of myiases in the treated and untreated groups. Abundance of fly larvae in naturally-voided dung pads and the survival of a species of dung beetle, Onthophagus sagittarius, were used to assess the effects of drug residues on the dung fauna.

RESULTS AND CONCLUSIONS

Moxidectin showed no activity against larvae of OWS during the first 14 days after treatment. Eprinomectin provided protection for 3 days after dosing, but failed at days 7 and 14, whereas doramectin was effective at day 7, but not at days 14 or 21. In contrast, no myiases were established on bolus-treated cattle from 14 to 102 days after treatment. Faecal residues of moxidectin had no effect on the survival of larvae of dung-feeding flies, whereas those of eprinomectin and doramectin reduced survival for 1 to 2 weeks. Dung voided by bolus-treated cattle inhibited fly breeding and had adverse effects on the development and survival of O sagittarius for up to 15 weeks after treatment.

Persistent activity of doramectin and ivermectin in the prevention of cutaneous myiasis in cattle experimentally infested with Cochliomyia hominivorax

A study was conducted to evaluate the activity of a single administration of doramectin or ivermectin against severe, induced infestations of Cochliomyia hominivorax. Twenty-four Holstein bull calves were allocated to four groups of six animals each and treated either with saline, doramectin 1%, or either one of two formulations of ivermectin 1% at a dose rate of 200 microg/kg. On Day 12 after treatment, each calf was anesthetized and two wounds were created on the left side of the shoulder and rump of each calf and 2 h later, each wound was implanted with 100 newly hatched larvae of C. hominivorax. On Day 15 after treatment, the procedure was repeated on the right side of each calf. Wounds were examined daily for 5 days and evidence of live larvae was recorded. Doramectin provided reduction in myiasis of 90.9 and 83.3% at 12 and 15 days after treatment, respectively, compared to the saline control treatment (P < 0.0001). In contrast, there were no significant differences in the number of calves with myiasis between those treated with either of the ivermectin formulations and the saline control.

Field efficacy of doramectin pour-on against naturally-acquired, gastrointestinal nematodes of cattle in North America

Seven studies were conducted under field conditions in North America to evaluate the therapeutic efficacy of doramectin in a pour-on formulation at a dosage of 500 microg/kg (1 ml/10 kg) for cattle harboring naturally-acquired infections of gastrointestinal nematodes, including species of Haemonchus, Ostertagia, Trichostrongylus, Bunostomum, Cooperia, and Oesophagostomum. In each study, 40 to 100 cattle were randomly allocated to a saline- or doramectin-treated group in a tiered manner based on Day -7 bodyweight. On Day 0, the cattle received either saline or doramectin topically, according to their treatment group. Weather and safety observations were made following treatment. No adverse reaction to treatment was observed at any time during these studies. Fecal egg count (FEC) determinations were carried out on each animal on Days -7, 0, 7, 14, and 21. Reductions in FEC for the doramectin-treated animals compared to saline-treated cattle were > or = 96.0% by Day -7 and > or = 99.0% on Days 14 and 21 for each study. Across all studies regardless of weather conditions, the reduction by Day 21 for the doramectin-treated animals compared to saline controls was 99.7% (p < or = 0.0001) and compared to pretreatment levels in doramectin-treated cattle was 99.9% (p < or = 0.0001). Doramectin pour-on should provide a useful new treatment for controlling nematode parasites of cattle.

Field efficacy of injectable doramectin against Chorioptes bovis in naturally infected cattle

A single subcutaneous injection of doramectin at a dose rate of 200 micrograms/kg bodyweight was effective in controlling an infection of Chorioptes bovis mites in naturally infected cattle. From 14 days after treatment, the geometric mean number of live mites was significantly lower (P < 0.001) in the doramectin-treated cattle than in the control group at each sampling until day 35. The percentage efficacy (treated versus controls) of doramectin against C bovis at day 35 was 99.9 per cent and the percentage reduction (day 35 versus day 0) in the treated animals was 99.3 per cent. At day 35, all seven controls were still positive for C bovis whereas five of the eight doramectin-treated animals were free of live mites.

Protective efficacy of doramectin and ivermectin against Cochliomyia hominivorax

Two studies were conducted in Brazil using induced infestations of the New World screwworm, Cochliomyia hominivorax, to investigate: a) the comparative prophylactic efficacy of doramectin and ivermectin at their recommended use levels (200 micrograms kg-1 s.c.), and b) the duration of protection of a single injection of doramectin. In the comparative efficacy study, two groups of six animals each were treated with ivermectin or doramectin. Two hours after treatment, four incisions were made. Each incision was infested with 30 first instar C. hominivorax larvae and their status evaluated daily for 7 days post-treatment (p.t.). Doramectin treatment was 100% effective in prevention of C. hominivorax infestations whereas ivermectin efficacy was incomplete. First instar larvae were eliminated in doramectin-treated calves by 48 h p.t., while in the ivermectin group, C. hominivorax developed in over 29% of the incisions. Healing began in wounds of doramectin-treated animals at 24 h p.t. and was in progress in 100% of all wounds at 2 days p.t., while 50% of ivermectin-treated calves showed incisions with active lesions. In the duration of protection study, 24 calves were allocated to six groups (T1-T6) of four animals each. Three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. Animals were infested as described previously according to the following schedule: T1 and T2 at day 14, T3 and T4 at day 21, and T5 and T6 at day 28 p.t. Incisions were evaluated daily for 8 days post-infestation. Screwworm infestations and viable third-instar larvae developed of all incisions of saline-treated calves, while doramectin was 100% effective preventing development of C. hominivorax for 21 days p.t. and showed partial activity at 28 days p.t.

Efficacy of injectable doramectin in the protection of castrated cattle against field infestations of Cochliomyia hominivorax

Three studies were conducted in Latin America--one in Venezuela, one in Argentina and one in Brazil--using a common protocol to investigate the efficacy of a single subcutaneous injection of doramectin in the prevention and control of Cochliomyia hominivorax infestations in castrated cattle. In each study, two groups of 20-28 animals each were allocated to a treated (T1) or to a control (T2) group on the basis of body weights. Animals of T1 received doramectin at 200 micrograms kg-1 (1 ml per 50 kg) and animals of T2 received saline solution at 1 ml per 50 kg of live weight. After treatment all cattle were castrated surgically. Animals were examined on treatment day and at 2, 4, 6 and 12 days post-treatment. At each observation day, the presence of C. hominivorax infestations was recorded. Doramectin was 100% effective in the prevention and control of screwworm strikes in castrated cattle exposed to continuous field infestations of C. hominivorax in tropical and subtropical areas of Latin America. Over the 12 day duration of the studies, 85%, 60% and 65% of animals in the control groups had infested wounds in Venezuela, Argentina and Brazil, respectively. Affected animals required repeated therapeutic treatment, whereas none of the doramectin-treated cattle were infested (P < 0.0001). A high proportion of the castration wounds in doramectin-treated cattle had the presence of characteristic C. hominivorax eggs but none developed into larvae. There were no clinical signs of adverse reactions to treatment in any of the three studies.

Efficacy of doramectin in the protection of neonatal calves and post-parturient cows against field strikes of Cochliomyia hominivorax

Two studies were conducted in Latin America, one in Venezuela and one in Argentina, using a common protocol to investigate the efficacy of a single s.c. injection of doramectin in the prevention and control of field infestations of Cochliomyia hominivorax in newborn calves and post-parturient cows. In both experiments, pregnant cows were paired on the basis of their calving time. The first cow that calved was assigned to a medicated group, and both cow and calf were treated with doramectin. The cow received a dose of 200 micrograms kg-1 and the calf 1 ml of a 1% doramectin solution. The second cow and calf were assigned to a saline-treated group, and the cow received saline at 1 ml per 50 kg and the calf 1 ml. The procedure was repeated until all animals were allocated to the two treatments. Animals were examined on the treatment day and at 2, 4, 6 and 12 days post-treatment. At each observation day, the navel of newborn calves and external genitalia of the cows were inspected and the presence of C. hominivorax infestations was recorded. Doramectin was 100% effective in the prevention and control of screwworm strikes in newborn calves and in post-parturient cows exposed to continuous field challenge of C. hominivorax. Over the 12 day duration of the studies, 48% and 57% of the saline-treated calves had screwworm navel strikes in the studies in Venezuela and Argentina, respectively. Infested animals required repeated therapeutic treatment, whereas none of the doramectin-treated calves were affected (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Strategies for the control of one-host ticks and relationship with tick-borne diseases in South America

A variety of hemoparasites occurs in ruminants of South America (12 degrees 00'N-56 degrees 00'S), but there is consensus on the significant economic impact of babesiosis (Babesia bovis and Babesia bigemina) and anaplasmosis (Anaplasma marginale). The tick vector for the Babesia spp. for the whole region is Boophilus microplus which has been the most important target in control/eradication programs. Boophilus microplus and many different hematophagous diptera species are considered vectors of A. marginale. In areas where babesiosis and anaplasmosis are present, the wide range of climates (tropical, subtropical, temperate), husbandry practices (subsistence, extensive, intensive), and tick control strategies has led to the concepts of enzootic stability and instability. Within this framework, six control strategies for Boophilus microplus can be identified: (1) absolute tick control--with the establishment of quarantine areas and the implementation of state legislation; (2) absolute tick control in marginal areas--using local epidemiological knowledge, strategic treatments, quarantine areas and the intervention of the state; (3) prophylactic treatment--with a predetermined acaricide treatment schedule aimed at reducing tick burdens to an acceptably low level; (4) threshold treatment--acaricides are applied by the farmer whenever the number of ticks on cattle exceed a threshold level; (5) opportunistic treatment--acaricides are applied when cattle are assembled for other purposes; (6) integrated tick control--principally involving the combination of acaricides with the use of tick-resistant crossbred cattle.

Therapeutic and persistent efficacy of doramectin against Dermatobia hominis in cattle

One therapeutic and one persistent efficacy study were conducted in Brazil to evaluate doramectin at a dose rate of 200 micrograms/kg-1 against induced infestations of the tropical warble-fly, Dermatobia hominis. Doramectin was very effective in both the treatment of established infestations and also in the prevention of damage caused by the parasite. In the therapeutic trial, 12 calves were infested along the dorsal line with 25 first instar larvae of recent field isolates of D. hominis but in one calf nodules did not develop. Twenty-four days later animals were allocated to two groups on the basis of the number of parasite nodules present. Six calves were treated with doramectin, and five received saline solution. Animals were examined daily for 11 days post-treatment and the number of nodules mapped and recorded. Larvae that completed development were collected and incubated to evaluate viability. In the persistent efficacy study, 24 calves were allocated to six groups (T1-T6) of four animals each. On the day of treatment, three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. At 21 days, 28 days and 35 days post-treatment, 25 first instar D. hominis larvae were seeded along the dorsal line of each calf of T1 and T2, T3 and T4, and T5 and T6, respectively. Animals were examined daily for 18 days and the number of nodules mapped and recorded 6, 12 and 18 days post-infestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic and persistent efficacy of doramectin against Boophilus microplus in cattle

One therapeutic and one persistent efficacy study were conducted in Brazil to evaluate doramectin at a dose rate of 200 micrograms kg-1 against induced infestations of the single host tick, Boophilus microplus. Doramectin was highly effective in eliminating established tick populations from cattle and also in preventing infestation by the parasite. In the therapeutic study, 12 calves were infested three times a week along the dorsal line with 2500 recently hatched larvae, for a total of 11 times before treatment. Animals were allocated to two groups on the basis of uniformity of established engorged tick burdens. Six calves were treated with doramectin and six received saline solution. From Day -3 to Day 21 post-treatment, individual collections of detached engorged female ticks were made from each calf. In the persistent efficacy study, 12 calves were allocated to two groups of six animals. Six calves were treated with doramectin and six received saline solution. From Day 1 to Day 17 post-treatment, each animal was infested three times a week along the dorsal line with 2500 recently hatched Boophilus microplus larvae, for a total of nine times. From Day 18 to Day 42 post-treatment, daily collections of detached engorged female ticks were made from individual animals. In the therapeutic study, efficacy (reduction of collected engorged female ticks) progressed from 51% at 24 h post-treatment (p.t.) to at least 99% at 4 days p.t., and reached 100% at 8 days p.t. With the exception of one tick that did not lay eggs, recovered from one animal at 11 days p.t., no more ticks were recovered from doramectin-treated calves for the duration of the experiment. For the first 6 days after treatment, only a few detached engorged ticks were collected from treated animals, and their oviposition and hatchability declined rapidly. In the persistent efficacy study, doramectin treatment was highly efficacious in preventing the establishment of Boophilus microplus populations for 20 days after the first ticks completed their cycle in the non-treated group. The oviposition and hatchability of the few ticks that completed their life cycle in the doramectin group were severely reduced.