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Moxidectin steady state prior to inoculation protects cats from subsequent, repeated infection with Dirofilaria immitis.

Little SE, Hostetler JA, Thomas JE, Bailey KL, Barrett AW, Gruntmeir K, Gruntmeir J, Starkey LA, Basel C, Blagburn BL - Parasit Vectors (2015)

Bottom Line: Blood samples were collected from each cat from 1 month prior to treatment until 7 months after the final inoculation and tested for antibody to, and antigen and microfilaria of, D. immitis.Cats treated with topical 10% imidacloprid-1% moxidectin prior to trickle inoculation of D. immitis L3 larvae throughout the 28 day post-treatment period remained negative on antibody and antigen tests throughout the study and did not develop gross or histologic lesions characteristic of heartworm infection.Microfilariae were not detected at any time.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA. susan.little@okstate.edu.

ABSTRACT

Background: Infection of cats with Dirofilaria immitis causes seroconversion on antibody tests and pulmonary pathology, often without subsequent development of adult heartworms. Consistent administration of topical 10% imidacloprid-1% moxidectin has been shown to result in sustained plasma levels of moxidectin in cats after three to five treatments, a pharmacokinetic behavior known as "steady state".

Methods: To evaluate the ability of moxidectin at "steady state" to protect cats from subsequent infection with D. immitis, cats (n = 10) were treated with the labeled dose of topical 10% imidacloprid-1% moxidectin for four monthly treatments. Each cat was inoculated with 25 third-stage larvae of D. immitis 7, 14, 21, and 28 days after the last treatment; non-treated cats (n = 9) were inoculated on the same days, serving as infection controls. Blood samples were collected from each cat from 1 month prior to treatment until 7 months after the final inoculation and tested for antibody to, and antigen and microfilaria of, D. immitis.

Results: Measurement of serum levels of moxidectin confirmed steady state in treated cats. Cats treated with topical 10% imidacloprid-1% moxidectin prior to trickle inoculation of D. immitis L3 larvae throughout the 28 day post-treatment period remained negative on antibody and antigen tests throughout the study and did not develop gross or histologic lesions characteristic of heartworm infection. A majority of non-treated cats tested antibody positive by 3-4 months post infection (6/9) and, after heat treatment, tested antigen positive by 6-7 months post-infection (5/9). Histologic lesions characteristic of D. immitis infection, including intimal and medial thickening of the pulmonary artery, were present in every cat with D. immitis antibodies (6/6), although adult D. immitis were confirmed in only 5/6 antibody-positive cats at necropsy. Microfilariae were not detected at any time.

Conclusions: Taken together, these data indicate that prior treatment with 10% imidacloprid-1% moxidectin protected cats from subsequent infection with D. immitis for 28 days, preventing both formation of a detectable antibody response and development of pulmonary lesions by either immature stages of D. immitis or young adult heartworms.

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Related in: MedlinePlus

Mean levels of moxidectin (μg/L) prior to and during repeated infection withDirofilaria immitis. Cats were treated with 10% imidacloprid-1% moxidectin on study days −84, −56, −28, and 0. Third-stage larvae of D. immitis (n = 25) were inoculated on days 7, 14, 21, and 28, 1 – 4 weeks after the final treatment was administered.
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Fig1: Mean levels of moxidectin (μg/L) prior to and during repeated infection withDirofilaria immitis. Cats were treated with 10% imidacloprid-1% moxidectin on study days −84, −56, −28, and 0. Third-stage larvae of D. immitis (n = 25) were inoculated on days 7, 14, 21, and 28, 1 – 4 weeks after the final treatment was administered.

Mentions: Mean trough levels of moxidectin in samples collected from treated cats on study days −85, −57, −29, and −1, prior to first inoculation with D. immitis, were as follows: none detected, 16.5, 33.4, and 40.0 μg/L, respectively (Figure 1). Mean levels of moxidectin during the repeated inoculations with D. immitis at study days 7, 14, 21, and 28 were as follows: 65.2, 53.6, 49.0, and 44.8 μg/L, respectively. Moxidectin was not detected in samples from non-treated control cats at any time point.Figure 1


Moxidectin steady state prior to inoculation protects cats from subsequent, repeated infection with Dirofilaria immitis.

Little SE, Hostetler JA, Thomas JE, Bailey KL, Barrett AW, Gruntmeir K, Gruntmeir J, Starkey LA, Basel C, Blagburn BL - Parasit Vectors (2015)

Mean levels of moxidectin (μg/L) prior to and during repeated infection withDirofilaria immitis. Cats were treated with 10% imidacloprid-1% moxidectin on study days −84, −56, −28, and 0. Third-stage larvae of D. immitis (n = 25) were inoculated on days 7, 14, 21, and 28, 1 – 4 weeks after the final treatment was administered.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4340871&req=5

Fig1: Mean levels of moxidectin (μg/L) prior to and during repeated infection withDirofilaria immitis. Cats were treated with 10% imidacloprid-1% moxidectin on study days −84, −56, −28, and 0. Third-stage larvae of D. immitis (n = 25) were inoculated on days 7, 14, 21, and 28, 1 – 4 weeks after the final treatment was administered.
Mentions: Mean trough levels of moxidectin in samples collected from treated cats on study days −85, −57, −29, and −1, prior to first inoculation with D. immitis, were as follows: none detected, 16.5, 33.4, and 40.0 μg/L, respectively (Figure 1). Mean levels of moxidectin during the repeated inoculations with D. immitis at study days 7, 14, 21, and 28 were as follows: 65.2, 53.6, 49.0, and 44.8 μg/L, respectively. Moxidectin was not detected in samples from non-treated control cats at any time point.Figure 1

Bottom Line: Blood samples were collected from each cat from 1 month prior to treatment until 7 months after the final inoculation and tested for antibody to, and antigen and microfilaria of, D. immitis.Cats treated with topical 10% imidacloprid-1% moxidectin prior to trickle inoculation of D. immitis L3 larvae throughout the 28 day post-treatment period remained negative on antibody and antigen tests throughout the study and did not develop gross or histologic lesions characteristic of heartworm infection.Microfilariae were not detected at any time.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA. susan.little@okstate.edu.

ABSTRACT

Background: Infection of cats with Dirofilaria immitis causes seroconversion on antibody tests and pulmonary pathology, often without subsequent development of adult heartworms. Consistent administration of topical 10% imidacloprid-1% moxidectin has been shown to result in sustained plasma levels of moxidectin in cats after three to five treatments, a pharmacokinetic behavior known as "steady state".

Methods: To evaluate the ability of moxidectin at "steady state" to protect cats from subsequent infection with D. immitis, cats (n = 10) were treated with the labeled dose of topical 10% imidacloprid-1% moxidectin for four monthly treatments. Each cat was inoculated with 25 third-stage larvae of D. immitis 7, 14, 21, and 28 days after the last treatment; non-treated cats (n = 9) were inoculated on the same days, serving as infection controls. Blood samples were collected from each cat from 1 month prior to treatment until 7 months after the final inoculation and tested for antibody to, and antigen and microfilaria of, D. immitis.

Results: Measurement of serum levels of moxidectin confirmed steady state in treated cats. Cats treated with topical 10% imidacloprid-1% moxidectin prior to trickle inoculation of D. immitis L3 larvae throughout the 28 day post-treatment period remained negative on antibody and antigen tests throughout the study and did not develop gross or histologic lesions characteristic of heartworm infection. A majority of non-treated cats tested antibody positive by 3-4 months post infection (6/9) and, after heat treatment, tested antigen positive by 6-7 months post-infection (5/9). Histologic lesions characteristic of D. immitis infection, including intimal and medial thickening of the pulmonary artery, were present in every cat with D. immitis antibodies (6/6), although adult D. immitis were confirmed in only 5/6 antibody-positive cats at necropsy. Microfilariae were not detected at any time.

Conclusions: Taken together, these data indicate that prior treatment with 10% imidacloprid-1% moxidectin protected cats from subsequent infection with D. immitis for 28 days, preventing both formation of a detectable antibody response and development of pulmonary lesions by either immature stages of D. immitis or young adult heartworms.

Show MeSH
Related in: MedlinePlus